Blending Modes Cookbook
There are very few books dedicated to Blend Modes, one of Photoshop's least understood but most useful features. I have been exchanging emails with John Beardsworth for a few years now, mostly relating to scripting and catalogues, but only recently found that he is the author of some excellent Photoshop books including this one dedicated to Blend Modes.
My favourite book on advanced Photoshop methods is Channel Chops by David Biedny but that's out of print. John's book does not exactly cover the same ground but it does offer a lot of information about the bewildering array of blend modes found with many of the Photoshop tools and there were a couple of subtleties that I was not aware of. Did you know, for example, that Hard Mix can be used for an interesting sharpening effect? Or that Lighten can be used to remove dust spots from skies? Read this book and learn all about blend modes - highly recommended.