Butterflies and Moths
Robert T. Mitchell, Herbert S. Zim, Andre Durenceau
Paperback
(Golden Press, Jan. 1, 1964)
This golden guide is an excellent place to learn the basics. It's small, therefore portable, and pictures often show male and female variations, different coloration phases and a view of wings spread and folded. It also contains range maps and pupa and larva pictures for most butterflies and moths. Keep in mind, though, that pictures are artist renderings, not photos.