My friend Jan Svenungsson recently published an excellent book about writing for artists that will surely be of interest to all creative people who are thinking about writing about their own work: An Artist's Text Book.
The book is available from the Finnish Academy of Fine Arts (because that's where he taught the course that led to the book):
Finnish Academy of Fine Arts
att: Anna Herlin
or by email: firstname.lastname@example.org
I proofread the book for Jan, and I assure you that it is an excellent read! (There's a quote from it here.)