The book is always, always, 100% better than the movie, even if the book sucked.
Why, you ask?
Because the movie will never be able to cram in every glorious aspect of the book. Take the "Harry Potter" series, for example: A series of movies so impossibly well done, in fact, probably still to this day some of the best book-to-movie-adaptations I've ever seen, but still missing beautiful, key scenes that only movie goers wouldn't know.
For instance: How Norbert the Dragon actually left Hogwarts. Or Dobby popping up and lending his house-elf wisdom over the years of the Golden Trio's adventures (because no, he did not disappear in between Chamber of Secrets and The Deathly Hallows. He did a lot). You wouldn't have read that heart-rending scene about Neville's parents or know where Gilderoy Lockhart ended up.
And you definitely would notice the difference between "Harry, did you put your name in the Goblet of Fire?" and "HARRYDIDYAPUTYANAMEINTHEGOBLETOFFIYAHHHH?"
Just a few examples of a lot. There's a reason "Order of the Phoenix" is like, the size of a refrigerator.
I thought of this random fact of life as I finished reading Stephen King's "It" this morning. Well, as close to the end as I could get, anyway. My parent's copy is missing its last 15 pages- that was heartbreaking to realize. And even though, years ago, I actually watched the movie (the old one, not the remake) and could remember some semblance of how the story ends, I was actually still really upset. "What if they changed the ending?" I thought wildly. It wouldn't be below King to do that- make me think everything might actually end all right for once and then twist to reveal that, ha ha, it's not (his other book "Pet Sematary" makes a notable inprint on my mind).
If everything ends the way I think it ends, then I might actually sleep soundly tonight. But Stephen King is Stephen King- he's not exactly known for warm fuzzy stories. His is the name that many understand to be synonymous with the words "horror" and "fear" and "tears," and "It" was no exception. If you can last through the gruesome murders at the beginning of the book and make it to the gruesome details of the middle of the book and make it to that now famous scene that many people lost their minds over the possibility of appearing in the movie (hint: it's children doing inappropriate things) than you can make it to the end, which is actually a lot better than the rest of the book. For once, I wasn't broken out in chills.
But I digress.
It doesn't matter if you read the book before or after you watch the movie- heck, it doesn't even matter the size of the book! But if you leave a theater or click out of a movie on Netflix and you think "wow, what a fantastic movie," and you KNOW that it's a film adaptation- then by all means, read the book.
Go to a bookstore, use Kindle Unlimited, or even use your local library. Most libraries offer a free library card to residents of their county.
I know the "Song of Ice and Fire" books are huge, but, yowza, if you love the "Game of Thrones" series, than by all means, read the books. You'll at least see the differences between the characters the authors pictured and how they're portrayed on screen (read: they're astounding at times).
If reading isn't your thing, dude, I get it.
But if it is... well. Come float with us.
And maybe if you're lucky, you'll float too.