No disrespect to La Vish, but I really don't understand this whole obsession with covers. Tech book covers rarely have anything to do with their contents. O'Reilly uses animals, Manning uses people in period dress, Head First uses hipsters. I have a PHP book with a sea anemone on the cover, an HTML5 book with a pointing hand, a cryptography book with a manhole cover, and an XML book showing Native American artwork.
Yes, I'm touchy about the subject as someone whose
book got a 1-star and a 3-star review on Amazon because they didn't like the samurai on the cover.