I have Quilting for Show, Secrets of Elemental Quilting and Custom Curves. I liked the Quilting for Show better of those, but I'm going to buy one of the curvy rulers and give the curved grid quilting a try, too. It's just such a striking look in some areas. :)
I had considered the one that's called Mastering McTavishing or something like that, but that seemed pretty one-techique-specific.
I don't usually need in-depth coverage of just one technique (and I may have been wrong on this point in the first place - maybe it covers a lot more!) but I would definitely go with Quilting for Show.
I haven't looked at it in quite a while, but as I recall, it was full of good ideas and it gives you enough of an idea of how things are done that you can get the gist of it.
I liked Elemental Quilting, too but it seems to be more technique-specific - and I'll bet I'll like it a lot more when I try trapunto or start trying to put together my own repeatable quilting motifs. So far, I'm just drawing little designs and tying them together with loops and squiggles.
Hope that helps! :) Happy quilting!