Clay and Glazes for the Potter by Daniel Rhodes
This classic text book, now in its third edition, is the best book I have found on the entire process of creating pottery.
ISBN: 0-87341-863-8
Clay and Glazes in Studio Ceramics by David Scott
Fairly comprehensive book on studio ceramics.
ISBN: 1 86126 138 1
The Kiln Book by Frederick L. Olsen
If you are planning to buy or build a kiln, you should get this book.
ISBN: 0-87341-910-3
The Ceramic Glazes Handbook by Mark Burleson
Describes glaze materials and processes. Lots of good pictures. Includes glaze formulas for various temperatures.
ISBN: 1-57990-202-2