Contacting the publisher would probably be a good start. They can define which rights they own and the author owns, and whether anyone is willing to sell you the adaptation rights.
Just for fun's sake, and if you haven't already done so, check imdb.com and see if a film is already being made (if it's such a good book, maybe you're not the only person who thinks this way?), check the author's site, the publisher's site, Google the title and author, etc. You never know what info you might turn up.
-Derek
-> * <- Click on this magic star to be transported to my website. Ruby slippers optional.
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The practice of art isn't to make a living. It's to make your soul grow. ~The Complete Handbook of Novel Writing (Kurt Vonnegut)