Doktor Faustus by Thomas Mann, is all about music, and is wonderful, but it is HEAVY!!!!!
Non-fiction, but Maynard Solomon's psychobiography of Beethoven is compelling -- and the final unravelling of the "Immortal Beloved" mystery is worthy of a good detective story.
H.C. Robbbins-Landon's, 1789, Mozart's Last Year, is heartbreaking, but beautifully written.
Any of Peter Guralnick's books, including the 2 volume biography of Elvis, especially volume 1, Last Train to Memphis, are well worth reading. I couldn't put them down (the ultimate accolade).
yours, Peter T.