[Warning: The following contains spoilers for the series premiere of HBO's His Dark Materials and for Philip Pullman's His Dark Materials and The Book of Dust trilogies. Read at your own risk!]

Fans of Philip Pullman's His Dark Materials novels have been waiting over 20 years to see a (good) adaptation of the celebrated trilogy, and on Monday HBO premiered its anticipated His Dark Materials series. Unlike HBO's other buzzy new show this fall, Watchmen, His Dark Materials isn't telling a fresh story set in a familiar universe but is setting out to be a faithful adaptation of Pullman's original work.

In the series premiere, titled "Lyra's Jordan," viewers are immediately immersed in the alluring world of the first book, The Golden Compass, in which humans have daemons (animal embodiments of their souls), there's a mysterious device can predict the troubled future of a daring and tenacious young girl, and something called Dust is either the greatest discovery or the downfall of all humanity, depending on who you ask. This episode did a solid job of laying the foundations of the world of His Dark Materials and who the major players are, but how does it compare to the books?

A Spoiler-Free Guide to the His Dark Materials Universe

TV Guide senior editors Sadie Gennis and Kaitlin Thomas are gathering together each week for a chat series for fans of Pullman's books. This is a safe haven to discuss spoilers and changes from the novels (both good and bad), so if you keep reading past this and get mad about learning some future twist, please don't say we didn't warn you.

Sadie: So what did you think of the series premiere? I know we've all been burned before by the movie we shall not speak of, but I really liked the first episode. It felt like finally we're getting the on-screen adaptation that these novels deserve. It just took us 24 years to get here!

Kaitlin: Yeah, I agree. I was cautiously optimistic once the cast was announced — it feels like Ruth Wilson was born to play Mrs. Coulter (is that mean? No offense, Ruth Wilson!) — and I'm happy to say that this feels like the adaptation fans have always wanted and hoped for. And I think it's satisfying because it's on television. This world is too rich and too deep for it to be successfully adapted for the big screen. By spreading out Lyra's (Dafne Keen) journey across multiple episodes and seasons, we're able to dig into things that movies would likely have skipped over.

His Dark Materials Review: HBO's Must-See Adaptation of Philip Pullman's Thought-Provoking Novels

Sadie: I know! And while I don't think any adaptation is ever going to fully capture the characters' interior worlds quite the way Pullman's original works do, I feel like the premiere did a great job establishing the main characters quite clearly, all while packing in so many great nods to The Golden Compass. We saw Lyra stealing wine, being disrespectful in the crypts with Roger (Lewin Lloyd), and running on the Jordan College roofs, and there's even a postcard taped up in her bedroom detailing the time she stole the Costas' boat! This Lyra feels exactly like how I always pictured the character in the books, but with one key exception: She doesn't lie enough!

Kaitlin: This version of Lyra definitely feels a bit... I was going to say tamer, but I don't know if that's the right word? She's still wild and mischievous, and she's altogether too clever for her own good, but she definitely doesn't lie as much as the character does in the books. And yet Dafne Keen brings a lot of what I loved about her performance in Logan to Lyra. She says a lot even when she's not speaking. You can see that her brain is always working, revealing how intelligent she is. And how she acts with and responds to both Lord Asriel (James McAvoy) and Mrs. Coulter also helps ground the story as it rushes through what is actually four chapters of the book. I almost couldn't believe that Lyra was leaving Jordan College with Mrs. Coulter by the end of the pilot and that we'd gotten to spend significant time with the gyptians too.

Sadie: I was so happy that we got to dive into so much of the gyptians storyline and culture already! And introducing them through the daemon ceremony was such a lovely way to bring them in. If the things that the show's writers continue to add to this world stay on the level of this gyptian ceremony, then this series will be a real treat for book fans. I also wasn't expecting to meet John Faa (Lucian Msamati), Farder Coram (James Cosmo), or Benjamin de Ruyter (Simon Manyonda) so early, but it was kind of a relief to get those introductions out of the way. Now that the stage is set to dive into the Gobblers more in depth, we can really get the storyline moving along!

Although there was one other little change in the gyptians storyline that had me concerned for poor Billy Costa (Tyler Howitt). Did you notice his daemon's name was Ratter? That's the same name Tony Makarios' daemon had, and Tony Makarios (aka the first boy we saw get taken by the Gobblers in the book) was clearly cut for the show. If they're combining Billy Costa and Tony Makarios into one character, then I'm really worried for Billy!

His Dark Materials Season 1 Will Include 'Treats' from Later Books

Kaitlin: It took watching the episode twice for me to catch that because it happened so quickly! Combining the two characters definitely makes sense in terms of condensing the narrative for the small screen, but I think you're right to be worried. It hints at a very grim future for this version of Billy Costa. Is he meant to suffer the same fate as Tony in the books? Is he going to be the victim of intercision? Or are we getting ahead of ourselves? I honestly don't know. But combining Tony and Billy into one character isn't the only major change from the books in this episode, at least as far as I could tell. Did you notice that Lord Boreal (Ariyon Bakare) is now an attractive, much younger man?

Sadie: OK, yes, we need to talk about this because I was so confused. It didn't click for me that the hottie with the serpent daemon was Boreal the first time I watched the episode because one, I wasn't expecting to meet him until Season 2, when I figured they'd dive into everything from The Subtle Knife. And two, he looks GOOD. No wonder Mrs. Coulter had a thing with Boreal! (Although, I'm pretty sure that the Boreal in the books looks nothing like Ariyon Bakare.) My newfound and highly problematic attraction to Boreal aside, how do you feel about the decision to introduce Boreal already and start weaving in these elements from the second book so early?

Kaitlin: At the risk of being the annoying "that's not how it is in the books!" person, weaving in elements from The Subtle Knife in the very first episode of the show caught me a bit off guard. But I also know that this is a visual medium and that the story can't just be told from Lyra's point of view (or Will's later on). The world(s) building has to start now, so it makes sense that the writers are seeding these ideas in along the way. What I absolutely don't understand or like is that they changed the alethiometer. Did you hate that as much as I did?

Sadie: Yes! I'm actually completely on board with slowly laying the foundation of The Subtle Knife storylines — at least for now -- so that the transition into Season 2 won't feel so jarring and so that the show can potentially flesh out characters (like Boreal and hopefully John Parry!) to make them feel as richly developed and as worthy of our emotional investment as the rest of the ensemble. But making the alethiometer square? Are you ^&(%#* kidding me?! This is where I draw the line. It just seems so unnecessary! It was always described as circular and when Pullman had a replica made in 2008 it was — you guessed it — circular! I'm sure people who didn't read the books (and probably a fair amount who have) can't comprehend why this is so upsetting to us, but I feel like, particularly after that abominable movie, His Dark Materials fans can get a bit touchy when they see things being changed for no discernible reason.

12 Shows That Are Trying to Be the Next Game of Thrones

Kaitlin: Yeah, I don't think I am a totally unreasonable person — I understand not everything is going to be translated perfectly from page to screen — but there is simply no reason for the alethiometer to be square. I feel like if there is one thing that book fans will be united about after watching the first episode, it will be their anger at this nonsensical change. Though I guess they might also be mad about the erasure of The Book of Dust, which I know is eating away at your soul right now.

Sadie: Wow, thank you for that perfect set-up and also for knowing me so well. Now, prepare for my rant: A lot of His Dark Materials fans probably didn't read or didn't even know about the new trilogy, The Book of Dust, that Pullman started publishing in 2017. The first book, La Belle Sauvage, is set 12 years before The Golden Compass and is all about a young boy, Malcolm Polstead, trying to protect the infant Lyra. It also greatly expanded on the character of Hannah Relf, who was briefly introduced in the book when Lyra met Mrs. Coulter for the first time. And while it would have been a fun Easter egg for Book of Dust fans to see Hannah Relf at the Jordan College dinner, that's ultimately a forgivable thing to scrap. What is not so easy to overlook is the complete Malcolm Polstead erasure!

For all of La Belle Sauvage, Malcolm risks his life (and gets shot! And has to commit murder!!!) to get Lyra to the safety of Jordan College, which he does with the help of his friend Alice Parslow and Lord Asriel. Malcolm is even the one who leaves the alethiometer with Lyra — not Asriel! I completely understand that it would have been extremely confusing for viewers to see Asriel show up at the college in the opening scene with two kids and then never see these characters again. But I can't help but feel bad that Malcolm and Alice worked so hard to save Lyra's life and now those sacrifices might not exist in the show's version of events.

Kaitlin: I completely understand your anger. While not exactly the same thing, I am still furious that the movie version of Harry Potter and the Order of the Phoenix changed the way Sirius Black died, therefore changing the nature of his death and what it meant to the ensuing story. It's an anger I will take with me to the grave. So like, I get it. You're allowed to be mad about this. But does this ultimately change the way you feel about the show so far? Because I feel like the good things (Asriel's comfy-looking sweater, Hot Lord Boreal, PAN!!!) far outweigh the bad.

Sadie: On my tombstone please make sure it's inscribed, "Sadie Gennis, She Wasn't Always Too Petty," because I am really rising above my baser instincts here. Although I would have loved a small Easter egg for Book of Dust fans like myself, I do understand why these changes were made and on some level even get that these choices are probably for the best. Overall, I think this was a fantastic way to kick off the show and it made me excited to see what they do next. The Golden Compass is a children's book, which is not really HBO's typical vibe. But they did such a great job making this a faithful adaptation while still giving it HBO's signature prestige edge.

Kaitlin: And they should get props for making talking animals look better than the live-action Lion King — and on a much smaller budget, too.

His Dark Materials airs Mondays at 9/8c on HBO.