I second/third the library option before purchase! I exhausted my local (small, small town) library's stock of soaping books (less than 1/2 dozen) and began ordering from other libraries via the Library Sharing system in place in our state. I expect many places have a Library Sharing system where you can borrow from a wide variety of libraries, thus finding more soaping books to evaluate.
Many of the books I read were not worth a second read, and certainly not worth ordering from a book store. None at my local library were anything more than eye candy, IMO. There were a couple I would have liked to actually purchase, so I started a wish list & periodically review that list. So far, the book I have by Dr. Dunn, Scientific Soapmaking, is the one I use the most for research. But for a beginning soap maker, it's a little too scientific. What a newbie needs is a bit more hands-on how-to-make soap.
The Anne Watson books are good resources. I also liked the books by Alicia Grosso, Cavitch, mentioned by dixiedragon above. I liked one of Faiola's books, Soap Crafting and may borrow that one again. I was not impressed with her Pure Soapmaking book, however.