Be aware that there are 9 books with ~4500 pages. I read these a long time ago...
I was lucky that I only read the first book ("The Gunslinger") around 2000, so I did not have that long to wait for the end of the story.
However, NOBODY I know who had both read the books and seen the movie had a favourable view of the movie. So - on a positive side - the books might be even more awesome than the movie, but they might also be targeted at different audiences. But I do think the books were awesome at the time and likely still are. Hell, I might even read those again, or watch the movie now ....
And, if you are in the mood for a lot of books, also look at this article that also puts other books King has written that are related to the story into the total reading order: