Different Types of adaptations of written works:
Same names, maybe one or two broad concepts, otherwise it's a completely different story - this can make it easier to enjoy the work as it's own thing, but unfortunately for the original lovers, they won't be getting a faithful adaptation and probably not another for years and years. Makes you wonder why they couldn't just make it a new story (we know it's because of money) Examples*: The Bourne Identity series, Blood & Chocolate, iRobot, Ella Enchanted, I Am Legend, Pride & Prejudice & Zombies, The League of Extraordinary Gentlemen, The Princess Diaries, World War Z, Love in the Clouds, Love of the Divine Tree)
It needed to be longer/shorter - making a novel into a movie meant sheering off a lot of interesting side-plots (poor Tom Bombadil and Goldberry!) or lengthening a book into an entire series (The Hobbit trilogy). This can be done well (writer understands how to snip), but more often it's done poorly (lost very important character development and plot)
Cannot stand on it's own two feet - characters actions and motivations are inexplicable unless you've read the original work. World-building is assumed and never explained. You read the original and spend the whole time going "Ohhhh"
Good Enough - but why did they leave out my favourite scene? (Timeline & The Time Traveler's Wife)
Captures the Spirit of the Original - may not be a perfect adaptation, but you really feel like the adapters loved the source material and tried their best to transfer it to another medium (Sense & Sensibility 1995, Warm Bodies)
Bane of your Existence as a Lover of the Original - if it was completely unfaithful it would be better, but if it's faithful enough, you'll spend the rest of your life fighting the incorrect portrayal of a main character (P&P 2005, Shy Boi Darcy) or explaining that the theme is actually completely different (Mansfield Park 1999)
Simplified the Themes Down to Pap - "You are the real monster" Frankenstein 2025
Foe Adaptation - did the creator hate the original work? Is this a complex and expensive revenge on their Gr 11 English teacher? Why did they make this if they dislike the original work so much!
Perfect Adaptation - does this unicorn exist? Captures the themes, vibe, and spirit of the original work while also keeping all your very favourite tiny scenes and characters. Everyone is cast like you imagine and the script is mostly taken straight from the source material.
*I only used examples that I've both watched and read