I completely disagree with those who say to read the book first.
The book is going to be more in-depth, contain more scenes (usually) that may not be in the film, and will fill in and enrich the film if read following.
If you read the book first you tend to spend the film comparing it with the book, expecting certain scenes to come up, finding yourself disappointed that they left out your favourite ancillary character, etc.
By viewing the film "fresh" you can enjoy the movie, and then deepen your appreciation for the material with the book.
I have found several times that having read the book first had ruined the movie for me, but never have felt the inverse - that viewing a film had ruined the book. And I often will read a book after having seen the film.
I remember sneaking into "Misery" after having read the book and being highly disappointed with the film, even though Kathy Bates looked pretty much like I imagined the character (even if Caan didn't) because a few things (minor things - it was a fairly complete adaptation) were different, didn't play out like I thought they should, etc.
Sometimes I wish I had never heard of Shakespeare before seeing Olivier's "Hamlet" for the first time.
Speaking of, I also am a firm believer of VIEWING plays of Shakespeare before you read them as text - which is of course their intention. They were meant to be seen performed.
I'm starting to think the same of novels.
But of course I'm biased, since I believe cinema to be humanity's greatest achievement and finest art form.