Reasons why the book is 10x better than this abomination of a movie
Book: Ella was a somewhat rebellious, playful, spunky girl that would try to fight her curse, despite the pain it caused her. She would also try to find ways around it.
Movie: She makes no effort to fight the curse and it often makes her look like an idiot.
Book: Ella narrates the story in first-person.
Movie: Eric Idle narrates the story unnecessarily in rhyme and dresses like a lame, medieval bard.
Book: Ella first met Prince Charmont at her mom's funeral after she'd run off to cry over losing her mom. They had a nice walk back to the burial site, and you could already see the affection showing between them. (Apparently Ella's mom was friends with a lot of people, including members of the royal court).
Movie: Ella first meets Prince Charmont when he was being chased by a bunch of fangirls (oh gee, shoving modern Hollywood shit into a fairy tale? Really?) and he forces her to be quiet while hiding with her, and surprised that she's the only girl in the kingdom who doesn't treat him like a god. There's no sign of affection between them at all.
Book: Ella's fairy godmother, Mandy, resembled an older, grandmotherly type, and was smart, sassy, wise, and wonderful to Ella, despite being bossy and ordering her around all the time when working in the kitchen together. Mandy was also good at explaining why using "big magic" was dangerous compared to using "small magic," and why Ella needed to find conventional ways to solve her problems.
Movie: Mandy is played by a skinny brunette (Minnie Driver) and is a sweet, but vapid, stupid, empty character that has little to offer Ella other than a talking book.
Book: Mandy gave Ella a magical book that would have a different story every time she opened it, or it would give her information she could use. Mandy could even write her magical letters in it. The book could even protect itself from being stolen by people like Hattie, by being extremely boring and uninteresting. The book looked like an ordinary, leather-bound tome, and did not directly talk to her with an audible voice.
Movie: Mandy gifts Ella a talking book called "Benny," which looks more like a gift box with a man's head in it. He's annoying, and whatever advice he gives is lost when Ella gets sick of him and throws him in the trash at least once. Talk about cheesy special-effects!
Book: Ella had a very selfish, asshole for a dad, who was also a traveling merchant, and he's the reason she was sent off to finishing school with Hattie and Olive, but he didn't marry Hattie and Olive's mom, Dame Olga, until over halfway through the book, so Hattie and Olive were not Ella's stepsisters at first. Ella was taught how to act and behave like a lady (despite her rebellious nature) and she actually did learn some stuff while there.
Movie: Ella's going to a local "college" to become the medieval fantasy equivalent of a "strong, educated, modern woman," or some garbage like that. It's her own idea, nobody else's and I don't think you see her dad at all in this movie.
Book: Ella made best friends with a sweet girl named Areida, who was from a country next door to Ella's, and Ella learned how to speak Areida's language better through her. They were solid friends throughout the book, even when apart.
Movie: Areida is a boring, secondary character that you see once at Ella's "college" and never again. She's about as interesting as a block of wood.
Book: The only real villains in the story are Ella's curse, and her stepfamily.
Movie: The movie throws in (in addition to Ella's curse and her stepfamily) a stupid evil uncle who's trying to keep the throne for himself and kill Prince Charmont. He rules the kingdom with an iron fist through a cheesy-looking magical staff, has a talking snake, and treats all the magical creatures like second-class citizens. He doesn't even die from the poisoned crown at the end! We see him during that stupid wedding number, riding around in a wheelchair with a bandage on his head.
Book: When Ella ran away and met the elves in the woods, they were a kindly, nature-oriented people who were wonderful craftsmen and gave her a beautifully scuplted wolf mug as well as a pony and supplies to last her until she got to the Giant's farm (she was searching for Lucinda to try and break her curse). She traveled alone during the first half of her journey.
Movie: Ella rescues an elf in a cornfield (guess they stole that from "Wizard of Oz,") who wants to become a lawyer, and the elves were acting like a bunch of singing, dancing, broadway show idiots dressed in leafy green clothes in the woods (an idea they probably stole from the Camelot scene in "Monty Python.")