I have a book called The Soapmaker's Companion by Susan Miller Cavitch and it has a lot of good information. Although I've never read any books by Anne Watson, I have heard very positive things about her books on soapmaking.
I own smart soap making by anne watson. Its a good basic book. But VERY basic. I would be interested in something that explores the intricacies of soapmaking. If I just want to learn a basic process I have the youtube.
Along with the books mentioned, there is a new book called, "The Complete Idoit's Guide to Making Natural Soaps" by Sally Trew with Zonella Gould that I like. It covers CP, HP, Melt & Pour, Goat Milk soap, colorants, EOs & FOs, and a chapter on how to use Soapcalc.net. It includes several basic soap formulas (with Palm oil as the main oil). But the primary source of soapmaking information is found on these forums where soapmakers share their experiences. And making soap yourself is a great way to learn.
I too have "The Soapmaker's Companion" along with many others but I got but I used this one the most. I really got most of my information off the internet. Swift Crafty Monkey has a terrific blog spot full of TONS of information. Not only soap but bath products too. Just google that name and her site will come up.
Also too suppliers usually have great information and formulas on their web sites!