I've been picking up random books about comics lately. Stuff about the careers of various people in the industry, as well as art books. Not 'draw this line here and construct a face this way' instruction books. No, more just me looking for insight into what other people have done.
I'm not interested in reviewing books because, to be honest, there are others out there who are much better at it than I am. Seriously. Still, I'd like to mention a few now and then, just to say, 'hey, these great resources are out there.'

So, for starters, there's this book I picked up last month called
The Art of Top Cow. Aside from 'The Magdalena' comic, I've never read anything published by Top Cow before. But, this book was sitting in the comic shop in the discount area and the art was too gorgeous to pass up.
The book itself is quite large, over 300 pages of full page, full color art. There are next to no words, however. Just little type in the margins mentioning what issue the cover is from. So, no interviews or words from the artists here. Which, is a little sad. Those are always a nice touch. I'd also have loved to see more of the work in sketch form for comparison, but that's just me.
Have I found it useful: Actually, yes. I'm really interested in seeing what others do when it comes to covers. I can't seem to come up with solid, eye-catching covers to save my life. I've had a few decent ones, but most fall flat of what I want. (I'm beginning to understand why a number of comics have an interior artist and a different cover artist.) It's been a good source for sparking ideas, as well as discovering new methods I like... such as how one guy draws flowing hair or how another shows movement in a cape.
It's a bit pricey - most of these art books are for some reason. The cover price is around $35, though if you look around, you should be able to find a copy for a little less. I got mine for around $13, so check your local shops and see what you can find. It's been out for a year or so now and it probably wasn't that big of a seller. Who knows, maybe you'll get lucky.
"Try to be inspired by something every day. Try to inspire at least one person every day."
-- Mihaly Csikszentmihalyi