There's two books available from Amazon but they both suck and focus as much/more on growing your own barley and brewing herbs. An over-focus on brewing pests, too if you ask me and not enough practical advice or information on trellis design.
The free info on the internet is FAR better than either of the two widely available books.
There's a free PDF floating around on running your own small-scale organic hop farm that's even better than either of those books, too.
-It's sad, but true; if someone writes a good book on growing hops it should sell well. (Heck the two crap books have sold pretty well.)
Adam