I've looked for slide books on and off over the years - I've never found one that could show me what I wanted to know, so I've never bought one.
Most seem to be getting you into the scales and try to explain what some of shapes etc are. I'm not that sort of guitarist, I never use tab, etc... I can work things like that out for myself and get impatient trying to figure out what the book is trying to tell me! But if you do use tab etc for standard tunings, I'm sure most of the books have got something for you.
What I wanted, and you need as well, is "slide technique" - how to actually get a decent tone out of the blasted thing. And there are lots of decent tones. As far as I can tell, the only way to get yours is to listen closely to (and watch, if you can) slide-players that you like, and then keep experimenting/practicing until your left and right hand technique starts to produce these tones.
I'm not sure there's a quick way of doing this, but with this in mind, I'd suggest getting one of the books that come with a DVD perhaps?
Hope that helps :D
