Butterflies of Houston and Southeast Texas by John and Gloria Tveten. This is a must for folks in the Houston area. While I wish it had more pictures of each butterfly, the descriptions of habitat and habits of each species are incredibly helpful for those trying to find butterflies they’ve not yet seen.
Kaufman Field Guide to Butterflies of North America by Jim P. Brock and Kenn Kaufman. This is the first book I picked up, so I have a soft spot for it. It is easy to navigate, and its sketches are clean and easy to use.
A Swift Guide to Butterflies of North America by Jeffrey Glassberg. This is probably the most popular butterfly guide. It uses actual pictures and gives a wealth of information about habitat and range.