In the past I've referred to certain books as "the bible", the final word in their field. Well C.J.J. Berry's First Steps in Winemaking is undoubtedly the home winemaker's bible. I first started winemaking as a student, to knock up large batches of cheap falling-over-juice, and I've had this book ever since then. The pages are heavily annotated (and stained) and there are other recipes scribbled on scraps of paper stuffed between its pages.
The book has hundreds of recipes, organised by month. This is a really neat feature because if the winemaking mood takes you, you can easily look up what is in season at the moment. In the winter months it gives recipes for things like wheat, tinned fruit, and Ribena wine. If you're searching for a particular recipe there's an index in the back.
Berry (who in life had a really impressive moustache) teaches you not only how to make wine, but also all the "whys". By following the book I developed an understanding of winemaking which allowed me to experiment with my own brews. I think my all time top success was a 5 gallon batch of "everything the greengrocer was chucking out on Saturday afternoon", which resulted in a fabulous wine very like a good Cabernet Sauvignon. Sadly I never wrote down the proportions and so the recipe was unrepeatable. But then again Berry advised me to always keep scrupulous records for this very reason, so the fault lies with the student, not the master.
I don't have any other winemaking books and I don't feel I need any. First Steps in Winemaking has everything I need.