Four* that stand out for me:
Parker's Buying Guide, 6th Edition: The first wine book that I ever bought - despite the complete lack of notes (or even scores) in the Germany section, it led me deeper into this hobby of sorts, familiarized me with a lot of wines and producers that I had never heard of. I never became the next great hedonist, and don't read it much these days, but it certainly made its impact in my formative years of exploring wine.
The Sotheby's Encyclopedia of Wine, 3rd Edition, by Tom Stevenson: This has been a favorite since I bought it five years ago. While I also own (and like) Jancis' Oxford Encyclopedia, I prefer the format and the approach of this one - it's more accessible, but hardly dumbed down, with valuable overviews of nearly all of the French AOCs and Vins de Pays that existed at the time of its publication.
Opus Vino, Jim Gordon, ed.: Another large book, comprised of very up-to-date overviews of top producers from around the world, even though it has been out for a couple of years now. Most of the contributing authors are lesser-known, younger, yet highly knowledge and credible up-and-comers.
Pretty much anything by Stephen Brook: Stephen is my favorite wine writer. His Liquid Gold got me heavily into sweet wines several years ago, and I have also really enjoyed his books on Sauternes and German wines, and his articles for Decanter magazine. (For someone who thinks that Decanter's focus on Bordeaux is hugely excessive, anything that Stephen writes on Bordeaux is a must-read for me.)