Probably there is a thread on this already, but: I recently read Lush Life (David Hajdu), a 1996 biography of Billy Strayhorn.
I thought it fleshed out Strayhorn the man quite well. My main criticisms: for me Hajdu spent too much time (at times multiple pages) on minor characters in Strayhorn's social orbit. I felt the book dragged in those passages. Also (and I don't hold the non-musician author accountable for this) I would have liked to have read a much more in-depth analysis of the nuts and bolts of what made Strayhorn such a unique composer. To Hajdu's credit there are interviews with his musical colleagues that give some insights. I think a study of Strayhorn the musician by a musician is sorely needed. He really is that important.
Where the book really succeeded for me was Hajdu's very detailed exploration on Strayhorn's complex relationship with Ellington. It is well worth reading for that alone.
What did you, who have read it, think?