2021 saw movies and TV adapting everything from hefty fantasy novels to Twitter threads, with results ranging from stellar to “let’s not.”

What, exactly, separates an amazing adaptation from a rage-inducing one? Honestly, there’s no one “right” way to adapt something. There are, however, a few important lessons to keep in mind, and the best (and worst) adaptations of the year make great teachers. Here are the 5 lessons we learned about adaptation in 2021.

1. Lean into what makes your source material unique

When you choose to adapt something, you’re acknowledging that there’s something special about the source material, something that makes it worth the time and effort (and money) spent putting it onscreen. This year, several films embraced what made their source material stand out, with great results.

Zola director Janicza Bravo incorporated social media into her film as a nod to its beginnings as a viral Twitter thread by Aziah “Zola” Wells King. You’ll hear the chirp of Twitter notifications interspersed through dialogue, and Zola (Taylour Paige) will often deliver lines straight from the original tweets right into the camera, as if we’re watching her thread in real time. While the heavily stylized approach can feel alienating at times, it still proves a fiendishly clever way to acknowledge Zola‘s internet notoriety.

Where Zola pays tribute to the internet, this year’s movie musical adaptations heavily honor their Broadway roots. In The Heights brings the magic of musicals to life with fantastic elements that enhance its musical numbers, like characters dancing on the side of a building or bolts of fabric unravelling from the sky. Similarly, tick, tick…Boom! and West Side Story stage their set pieces with appropriate theatricality and take advantage of how film can heighten the already heightened realities of musicals. (tick, tick…Boom! is also overflowing with musical Easter eggs for all the theater kids out there.) Contrast this with the less successful musical adaptation of Dear Evan Hansen, which skews so close to reality that the songs — which feel natural in a theater setting — feel out of place.

2. A good update can work wonders

Speaking of musicals, Steven Spielberg’s West Side Story is more than a straight-forward adaptation. It’s an update that works hard to surface the themes of the original and reconfigures some classic scenes. Mashable’s Kristy Puchko writes that “Spielberg and [Tony] Kushner understood that it’s not enough to bring back the book and the songs with a shiny new cast (even if it is one that’s actually cast with Latinx talent in the roles of Puerto Ricans!) This revival was an opportunity to reimagine a classic story in a way that honors what came before but also gives audiences a fresh insight.” West Side Story proves that if an adaptation can right the wrongs of its predecessor and bring something new to the table, it is most certainly worthy of being put to film.

3. Standalone novels continue to make great miniseries (movies, take note)

Some of 2021’s best miniseries, like The Underground Railroad, The Pursuit of Love, and Station Eleven, are based on standalone novels. The miniseries is an almost perfect form for adaptation: It’s long enough to move through a lot of plot and provide a satisfying arc for its characters, but it’s also short enough that it doesn’t outstay its welcome. (Would The Handmaid’s Tale have been better as a miniseries? Yes.)

This is not to say that we should abandon book-to-movie adaptations and pivot to a miniseries-only approach. There were some truly amazing film adaptations of books this year, including The Power of the Dog and Dune. However, there were also some films that may have benefited from having more time to breathe, like the overlong House of Gucci. Based on the book by Sara Gay Forden, the years-long saga of the Gucci family sounds like the perfect story to tell in a longer, episodic format.

5. Deviating from the books can be a good thing…

2021 saw multiple adaptations of sci-fi and fantasy novels straying a bit from their sources, with compelling effects. The Wheel of Time, based on Robert Jordan’s extremely long series, rightfully cuts quite a bit of material and broadens its character perspectives so we aren’t mainly seeing things from Rand’s (Josha Stradowski) point of view. It also adds new storylines foregrounding the powerful all-female Aes Sedai order and brings to life other scenes that we only hear about in the books. The final product is close enough to the books that it will satisfy long-time fans, but it’s different enough that it will pleasantly surprise them as well.

While The Wheel of Time cuts a lot of material, Foundation expands into brand-new territory. Isaac Asimov’s novels are collections of short stories and novellas spanning thousands of years, which makes them hard to adapt as a continuous story. The show ends up taking creative liberties in order to give Foundation more connective tissue than just “these stories all involve the Foundation.” These liberties include an entirely new storyline involving a dynasty of cloned Emperors, which resulted in one the year’s most compelling episodes, as well as the addition of characters from the Foundation prequels and more developed backstories for characters like Gaal Dornick (Lou Llobell). Thanks to many of these changes, Foundation feels more cohesive, with a fleshed-out universe and defined characters.

5. …but too much deviation can wear thin

The biggest problem with Foundation is that once it starts making changes, it can’t stop. The Terminus plot involving Salvor Hardin (Leah Harvey) and Anacreon is as far removed from its source material as possible, even diving into Star Wars planet-destroying-ship territory at one point in a departure from the tone of Asimov’s diplomacy-focused Salvor-centered stories. As a result, that plotline is the most unsatisfying part of Foundation, despite Harvey and their co-stars’ strong performances and the show’s stunning visuals. Good acting and effects can only make up for so much when a story goes south.

The same goes for Netflix’s live-action adaptation of classic anime Cowboy Bebop, which Mashable’s Alison Foreman critiques for changing elements of Jet’s (Mustafa Shakir) backstory and altering villain Vicious (Alex Hassell) and love interest Julia (Elena Satine) beyond recognition. Foreman writes, “I found the audacity of claiming this series as a Cowboy Bebop successor kept me from enjoying what it was doing well. I couldn’t see beyond the anime inspiration it was mangling.”

Projects like West Side Story and The Wheel of Time prove that adaptations can certainly make changes for the better, including updating outdated material, but go one step too far and you’re looking at something entirely unrecognizable. Whether an adaptation succeeds often depends on how well it balances the new and the familiar, and how well it understands its source material in the first place.