The Ultimate Desert Handbook by Mark Johnson
While not strictly about Big Bend, this book subtitled "A manual for desert hikers, campers and travelers" is a very sound work on all things to consider when going to the desert and about the only one I know of just about desert hiking and travel. Fairly recent, 2003, it covers the range from different deserts and plant life to water, equipment, etc. The sections on water and water treatment and navigation (including GPS) are very good. There is a whole chapter on Wildlife Observation and Desert Photography.
About Big Bend it says on page 14, "Big Bend National park in Texas is a wonderful example of pristine Chihuahuan landscape."
Here is a link to the table of contents at Amazon
http://www.amazon.com/gp/reader/007139303X/ref=sib_dp_bod_toc?ie=UTF8&p=S007#reader-link
