Books that I think should grace any professional digital photographer's bookshelf.
by Peter Krogh. Currently the bible of digital asset management and a required read for all digital photographers who are even remotely busy.
by Scott Kelby. If you have a particular retouching problem to solve, the procedure to use is probably in here.
to the Creative Use of Photoshop for the Macintosh and PC, by Martin Evening. If on the other hand you want to gain a deep understanding of Photoshop itself, this book can't be beaten.
by David Allen. Finally, a useful, systematic way of coping with all of the demands on your time and energy.
by Scott Kelby and Terry White. Full of answers to how-do-I questions, in Kelby's usual way.