Alex Hirsch’s The Book of Bill, the first Gravity Falls book for adult readers, proved immensely popular with fans when it hit store shelves last July. The illustrated novel (of sorts) debuted at No. 1 on The New York Times Best Seller list and remained on the list through the holiday season. Gravity falls fans who haven’t picked up Bill’s origin story, as told by him, can save 50% on the newly released collectible edition with a slipcase and numerous extras. Released September 23 for $40, The Book of Bill Limited Collector’s Edition is already discounted to only $20.54 at Amazon.

If you’re shopping for a Gravity Falls fan this holiday, the new edition would make for an awesome gift. The original hardcover edition wouldn’t be a bad gift either–unless they already have it, of course. The Book of Bill’s standard hardcover edition is on sale for only $10.67 (was $27) at Amazon, where it holds a 4.8/5 star average based on 5,300+ customer reviews.

$20.54 (was $40)

The Book of Bill Limited Collector’s Edition has a few stylish extras for Gravity Falls fans. Perhaps most notably, the hardcover is packaged in a glow-in-the-dark slipcase, and the artwork is presented in a color referred to as “Undead Green.”

Along with the book, you’ll find a double-sided poster, four postcards with appropriately bizarre art, and a sticker sheet with, yes, some strange stickers (six of them, to be exact).

If you already own a copy of the best-selling book, it’s worth reiterating that between the covers, this is the same 208-page book outlined below.

$10.67 (was $27)

The Book of Bill is a dark comedy told from the perspective of Gravity Falls villain Bill Cipher. Throughout the collection of illustrated stories and random asides, Bill details his origin story and influences, offers his opinion on his impact on humanity, provides a step-by-step guide to world domination, and more.

Like some other Gravity Falls books, The Book of Bill has riddles, puzzles, and plenty of zany nonsense. The cover art is a warning on its own, but it’s worth emphasizing that The Book of Bill’s illustrations and text are not for young Gravity Falls fans.

Though Gravity Falls was a Disney animated show, it had crossover appeal for adult viewers, so it’s not surprising that series creator Alex Hirsch wrote a book that caters toward older fans of the show. Plus, many fans who watched the show during its run are now adults with nostalgia for a favorite from their childhoods.

Take a closer look at the Collector’s Edition inserts and design below:

Gravity Falls earned a dedicated fanbase throughout its two-season run thanks to its whimsical characters, charming animation style, and off-beat storylines. Physical editions of the complete series have been out of print for years, with the Blu-ray edition in particular selling for high prices on the reseller market. You can get Gravity Falls: The Complete Series on DVD for $40 at Amazon. This is the Collector’s Edition 2018 release featuring all 40 episodes in widescreen format. If you search Amazon, you’ll likely come across Gravity Falls: Even Stranger, which is $20, but be aware this release only has eight episodes from Season 1.

As mentioned, The Book of Bill was the first Gravity Falls book for adults. A second Gravity Falls book for teens and adults was published in May. Gravity Falls: Don’t Color This Book! It’s Cursed! is a coloring book that is as cursed, or perhaps even more cursed, than The Book of Bill. You can buy the 64-page cursed paperback artifact for $8.80 at Amazon.

Here’s a list of Gravity Falls stories, activity books, and journals for young readers and writers.

Books for younger Gravity Falls fans

Gravity Falls fans should also check out this (unofficial) Mystery Shack building set. The 1,038-piece kit is $40 and has solid customer reviews.