Reddit mentions of Snakes: The Evolution of Mystery in Nature

Hmm, books are tricky. You'll have better luck looking up individual snakes. Here's a few of my favorites though.
https://www.amazon.com/gp/aw/d/0691124361/ref=mp_s_a_1_28?ie=UTF8&qid=1481930124&sr=1-28&pi=AC_SX236_SY340_QL65&keywords=snakes

http://www.barnesandnoble.com/mobile/w/snake-chris-mattison/1100488504?ean=9780756613655&st=PLA&sid=BNB_DRS_Core+Shopping+Books_00000000&2sid=Google_&sourceId=PLGoP62465

https://www.amazon.com/gp/aw/d/0520224876/ref=mp_s_a_1_16?ie=UTF8&qid=1481930293&sr=1-16&pi=SY200_QL40&keywords=snakes&dpPl=1&dpID=51haSGah73L&ref=plSrch

https://www.amazon.com/gp/aw/d/B0084ETQCC/ref=mp_s_a_1_1?ie=UTF8&qid=1481930435&sr=8-1&pi=SY200_QL40&keywords=handbook+of+venomous+snakes&dpPl=1&dpID=51cl0ph79uL&ref=plSrch


Those should do a pretty good job of keeping you busy. I tried to list them from most broad to most technical.

There are some good books out there to give as gifts that are valuable books to have in a professional library. I'd suggest Harry Green's "Snakes" http://www.amazon.com/Snakes-The-Evolution-Mystery-Nature/dp/0520224876 or Losos's Anole Book. http://www.amazon.com/Lizards-Evolutionary-Tree-Radiation-Environments/dp/0520255917

Those are written more like stories and contain pretty good science, so it's worth checking them out. Field guides are also great. The Peterson's Guides mentioned below are good. The Georgia book is also a great guide to the Southeast, and is a really good value for its size http://www.amazon.com/Amphibians-Reptiles-Georgia-Matt-Elliott/dp/0820331112. Kate Jackson has a book on field work that's not too bad but those others are better buys http://www.amazon.com/Mean-Lowly-Things-Science-Survival/dp/0674048423.

McDiarmid's reptile biodiversity book is on my shelf but it's not exactly a page turner. She probably wouldn't read it as much as use it as a reference. The others, she will.

There's also this one, which is good for a laugh! www.amazon.com/Culinary-Herpetologist-Ernest-Liner/dp/1932871063

I would recommend Snakes by Harry W Greene. A professor of mine gave it to me when I graduated. It is a beautiful book and has a ton of great information. Link to Amazon It only comes in paperback but it is a great book. If they are into going out and looking for herps I would recommend a field guide. Depending on where you are in the US there is a field guide, one for the Eastern and Central US and one for the Western US. The scientific names are outdated but the range maps and photos are still handy for learning about all of the herps in your area. Hope this helps!