I really like Ken Druse's Natural Shade Garden because it includes actual information about shade-loving plants in addition to images and discussion of good plant combinations. The photos are enchanting and plants are named in the captions.
Similar to the Druse book is Keith Wiley's Shade. This is a slightly slimmer book, and though I prefer the images in the Druse book, Shade has a great glossary of plants in the back for easy reference.
Both the above books draw inspiration from woodlands - as the plants that naturally occur in woodlands are tolerant of shade. And of course, woodlands (or most of them) are only really in shade after the canopy leafs out and until the leaves fall in autumn. A great book on woodland plants is Beth Chatto's Shade Garden.