I\'m studying the book called \"the study of orchestration\" by Samuel Adler, and I LOVE it! The main reason is the 5 cds set which you can buy and which contain almost every example scored in the book. Listening to those extracts is quite a pleasure and very helpful for me to determine my musical direction (hear what I like and what I don\'t!)
The cd set is a bit expansive, but it is definitely worth it, imho.
I have the Kent Wheeler Kennan and the Samual Adler books, but my favorite is Orchestration by Cecil Forsythe. It\'s a bit more in depth than the other books in terms of explaining the intricacies of specific instruments.