I have quite a few oil paintings books, and I consider Bill Creevy's 'The Oil Painting Book' to be one of the best reference books in my collection. It is also an interesting and informative book on oil painting techniques, such as glazing and scumbling (truly excellent on these topics), alla prima, wiping out method, and many more.
However, I have found it to be the most useful as a reference book for oil painting materials. Its section on oil paint brands is outstanding - not only are the major brands evaluated, but also the specialty small company brands. Particularly strong is the section on oil painting mediums. To me this is such a challenging area for someone beginning oil painting. This book thoroughly defines and discusses over 18 different mediums, which provides an excellent starting point for someone learning about oil painting. Nothing beats actually experimenting with the mediums yourself, but it helps to read about them beforehand to see what kind of effects they achieve.
I highly recommend this book.