Hugh Johnson is my kind of wine writer - he obviously possesses a great deal of knowledge about wine, how it is made, where it comes from, etc. But he also understands that the great majority of people who might drink a bottle of wine, or who might pick up his book, are not quite as knowledgable and familiar with various vinicultural terms. Accordingly, he has written a comprehensive, true "encyclopedia" of wine that has something for everyone.
If you are like me, you keep a book like this, and periodically pick it up after buying a few bottles at your local shop to read his tasting notes, or some information about the winery. The book is perfect for that, he included small profiles and/or tasting notes for thousands of wineries in virtually all major wine-producing countries. The list of California wineries alone, and Johnson's personal observations about their varietals, is staggering. He doesn't simply profile the big, million case producers but has notes about small, "boutique" wineries like Groth, etc. And aside from tasting notes, the book has a whole lot more to offer.
Johnson explains how various types of wine are made (port and champagne, for example), includes maps as well as biographical profiles of some leading personalities in the wine world (like Robert Mondavi), and explains in layman's terms which glasses to use, when some "experts" like to decant, etc. This is a book to have lingering around, not for a sit down, cover to cover reading but as a source of information, that can be supplemented every couple of years by purchasing Johnson's excellent annual pocket encyclopedias (with more up to date tasting and winery info). I find myself picking up the book to look up something specific, and unable to put it down for a half hour or more while I browse. Pick it up, for the price of a single bottle of Montrachet, you will enhance your knowledge and enjoyment of wine considerably.