Reddit mentions of Holy Smoke! It's Mezcal!: A Complete Guide from Agave to Zapotec

I'm going to actively try to avoid recipe books here in my links (that said, that means you're missing out on Vintage Spirits & Forgotten Cocktails, Death & Co, Potions of the Caribbean, and The Joy of Mixology so.... YMMV)

Liquid Intelligence - IMHO must have guide on the technical aspects of bartending. This book is amazing and is the first thing I share with my coworkers that want to broaden their knowledge

The Drunken Botanist - In depth examination of the plants that go into making our favorite drinks, beers, booze, and sundry

Bitters - Has history of bitters, along with instructional on how to make your own.

Shrubs Kind of recipes but also talks about how to make shrubs and good proportions for them, which isn't super common.

Wine Folly Do you want a good intro-to-wine with good, clear reference sheets about styles and pairings? Here's your book

The Wine Bible Want to know way more than you ever thought you wanted to know about wine? This is what you want to be reading.

The Beer Bible - Same as above, but for beer instead of wine.

Holy Smoke! Its Mezcal Mezcal can be hard to pin down and I've found this one to be decent. Includes a table of things that were available in the US at time of publishing and the author's opinions on quality.

Vermouth - pretty in depth history on vermouth, focusing on its place in American cocktail Culture

Imbibe! In depth history of early cocktail culture, focusing on Jerry Thomas and the Bon Vivant's Companion

...I'm sure I could think of more, given the time. I'm trying to just delve into things currently on my shelf, and not in my wishlist.