First, a solid base in Biology and Zoology. There are a number of good texts for that. I'm not sure if they are all still in print, but some are:
Worlds within Worlds An Introduction to Biology. It's a college level text by Thomas C. Emmel from The University of Florida, published by Harcourt Brace.
Exploring Biology by Pamela S. Camp and Karen Arms is an advanced High school level text published by CBS College Publishing
The Study of Biology (this one is probably out of print) by Baker-Allen. Published by Addison-Wesley. Excellent basic coverage of cellular biology.
Then a good book on basic Herpetology is Herpetology by Goin, Goin, Zug. W.H. Freeman Publishing Company. There are several editions to this text.
There are several more recent texts on the subject of Herpetology. One website that's worth checking out is www.krieger-publishing.com.
For online text and reference, check out: http://www.library.usyd.edu.au/subjects/biosci/bioscirefzoology.html
and
http://cellbio.utmb.edu/cellbio/
and
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookTOC.html