The book has so much more to offer than the movie, by all means read it first.
Having read the book, I was disappointed in the movie. It barely scratches the surface of the rich irony, satire and allegory that are sofundamental to the book. But maybe it's one of those books that no movie could do justice to anyway. Like Joyce's Ulysses.
I finally read the book and it has become one of my favorites. I'm looking forward to seeing the movie if I find it in my local video rental sites.
I'll also look for it's sequel 'Closing Time' next time I'm at a bookstore in the States.
