Well, these are my books that help ID butterflies (and some moths) and their caterpillars, as well as giving info about life cycle and such:
Butterflies through Binoculars, The West by Jeffrey Glassberg
National Audubon Society Field Guide to Butterflies
Caterpillars in the Field and Garden, a field guide to the butterfly caterpillars of North America by Allen, Brock, and Glassberg
Caterpillars of Eastern America, by David L. Wagner
And this is a truly great book that tells why we need native plant habitats in our yards or on our properties:
Bringing Nature Home, How You Can Sustain Wildlife with Native Plants by Douglas W. Tallamy
