we used to have a "recommended reading" section, but I can't find it now
for basic care there's David Perlowin, The General Care and Maintenance of Garter Snakes & Water Snakes, and Bartlett & Bartlett, Garter and Ribbon Snakes
and then, much less basic - Rossman et al, The Garter Snakes - Evolution and Ecology
I also highly recommend Bianca Lavies, A Gathering of Garter Snakes, and Sy Montgomery, The Snake Scientist - both primarily about the Narcisse snake dens.
If you're also interested in other North American Snakes, and you've got money, or folks who give you pricey gifts, I highly recommend Rossi & Rossi, Snakes of the United States and Canada: Natural History and Care in Captivity (right now there's a used copy available at Amazon for under $100 - something to jump on) - it's got about fifty pages on Thamnophis and almost that many on Nerodia
that ought to be enough to get y'all started
happy reading