Standard book contracts state very clearly that the publisher has the final say over title and cover art, which is how book covers sometimes aquire tent pegs for no apparent reason.
Sometimes, however, an author can make suggestions and the publisher agrees. Sometimes the publisher may be skeptical about the author's judgment, and sometimes the author may be skeptical about his own judgment, and sometimes everybody can be a little nervous about a title that's a little strange. Nevertheless, it is now official that my WPF (aka Avalon) book will have the totally cool title:
Applications = Code + Markup
A Guide to the Microsoft Windows Presentation Foundation
Of course, the title is an homage to Niklaus Wirth's classic 1975 text Algorithms + Data Structures = Programs, which I always thought was the best programming-book title ever. (The content is pretty good too!)
The other title I suggested to my publisher was even geekier. Imagine seeing this on the cover of a book:
Microsoft Windows Presentation Foundation
But there was a feeling this title might totally screw up some retailer's database.