vpFree
Dan Paymar's "Optimal Play Video Poker" is probably the best available. However, I think books are poorly suited for teaching vp concepts. I'd recommend following the discussions at the vpFree forum and purchasing one or more software programs for practice.
Software: "Frugal Video Poker" is quite good, but "WinPoker" seems easier for practice for many people (including me), but lacks a couple of the more advanced features of FVP. There are a couple of newer programs out as well, but I have no experience with them.