Scientific Soapmaking - Kevin Dunn is NOT a beginning soapmaking book. He is a university professor chemist who wrote this book to help understand the science behind soapmaking. It is not a beginning book by any means, but once you get beyond "I made soap!", and start to question "why" things happen, this is an excellent resource.
If you have a Kindle, there are quite a few free books out there. The Ann Watson series is good. Another resource for book recommendations is the HSCG - The Handcrafted Soap Makers Guild. They carry quite a few books in their store. They also have a relatively new section where they present basic videos on process.
Again - it was asked above - what are you looking for in a book? Recipes?, process? Bear in mind there is no one definitive recipe that is the best. There is no one method; new takes on designs and modified processes are being developed all of the time. Realizing you are handling chemicals and working safely is the only golden rule there is - Never, ever add water to lye is the only absolute I can think of.
Soaping is a journey. It challenges the mad scientist in all of us. It combines science and artistry. It never gets boring; it rewards patience. If you are thinking about a business opportunity, wonderful. Just realize it will take research, practice and business skills. You need to test your recipes, understand why you are using your chosen oils in your recipe. Once you add color and fragrance to the party, you add even more variables. There is a soaping language to learn.
The only formula I can give someone is read, watch, learn, do - repeat. If you choose to become a good student; parking here and reading as much as you can handle is a good start. Then start watching You Tube videos - It won't take long to figure out the better teachers out there. Finally, when you think you "have it", use a
soap calculator of your choice and plug in a recipe you find in a book, or create your own. Next step - shopping. Walmart, Dollar store, and Goodwill are good cost conscious options. Finally - make a basic soap without scent or color. If you start jumping up and down, want to tell, show everyone you know about your new-found obsession, then you are ready to move on. Take a class, go to a conference and make new soapy friends.
Then when you have the basic process down, start being more adventurous. Welcome to the journey.