Of course is worth it, besides Neil Gaiman is a terrific writer. I don´t know your age but I don´t recomend the book for kids. If you are a teenager or older, you should read it. Despite I really LOVE the movie, the book is even better, is darker and a lot scarier. The movie was made for kids so they were actually gentle adding bright colors, even in the most darkest scenes. I think you will enjoy it, and some things are going to have a more extended explanation. In the book you´ll find a braver Coraline, because there, Wybie doesn´t exist. Greetings!
Of course I recommend it. In my opinion, the book is so much better then the movie. It's kinda creepy though it's not scary creepy. The writing is like poetry, you know?