If you pick up any "Wine Buyer" that describes the region, winery, types and years of each wine to buy, they are speaking of the grapes grown in that region, and year the grapes are harvested and the weather. Since weather has a lot to do with how much sun/water the vines get, it will have an effect on the taste, etc. of a given wine. Also, keep in mind these books speak about the type of grape. One can also learn which grape variety can withstand some negative elements (too much rain, sun, cold, etc.) and will produce relatively well regardless.
Some years are too wet, or too dry for a region so more or less crop is produced. It is funny how the newer books hold old weather information. Once you know which winery grows what type of grape, you can pretty much keep an eye on the area as the year goes on.
Also, I found that once you buy a good book, there is no reason to get another for at least every other year.