Favorite all around wine reference book
Hands down, it's the Oxford Companion to Wine, by Jancis Robinson. Granted, it's not exactly a page-turner that you are going to read from beginning to end, but if you are even remotely an oenophile, you will want it on your coffee table or bookcase. Written in encyclopedia/dictionary form, everything is included, from grape varietals, to wine making terms, to vineyards and wine regions, to historical wine figures.
Take some of your tax refund, buy a case of wine and this book, and start "studying"!