Along with cocktails themselves, I love books about cocktails. In general, I tend to be a cocktail purist, so I stay away from most modern books about drinks. For example, it makes me bonkers to see weird, frou frou cocktails called "martinis" just because they are served in a martini glass. A "martini" is gin, a drop of vermouth, and an olive. It is only very recently that I have acknowledged the "vodka martini" because I always considered this drink to be a "vodkatini" -- a poor second cousin to a true martini.
I have turned to vintage cocktail books because I like reading the informative sections, especially the advice on how to host parties, and trying out the old drink recipes -- classics and those that have not managed to stand the test of time. These books are generally out of print, but often found in used books atores or eBay. My favorites are:
Trader Vic's Bartender Guide
Esquire's Handbook for Hosts
Patrick Duffy's The Official Mixer's Manual