"...Do you have any book you get this kind of information from?..."
Well, no, not exactly. I compile information from many sources, including old soap manufacturing books from the 1800s and early 1900s. These books are available for free from Project Gutenberg and Internet Archive, if you're interested.
But a lot of it comes from bits and pieces of information that I gather here and there and squirrel away in my head or on my computer. Most of the information comes from the research I do to answer questions that interest me -- often questions you all ask here at SMF. Sometimes I answer a question on SMF with the best information I have at the time, but I will often continue to research the topic for some time afterwards, so you'll see my answers evolve as I learn more and put small pieces of information together to create a better answer.
For example, one issue that comes up often at SMF is that coconut oil is more irritating to some people's skin than palm kernel oil. The Soapcalc fatty acid profiles are almost the same, so why is CO more drying or irritating than PKO? The short answer (I think) is that coconut oil has more capric and caprylic fatty acids than PKO. Why are those two fatty acids important to this issue? Soaps made from these short-chain fatty acids are going to be even more water soluble and even better at dissolving fats (aka drying out one's skin) than the myristic and lauric acids.
Digging out that answer has led me to wonder what other fatty acids might be overlooked by the soaping calculators, so I'm working, as I have the inclination, to create a table of the approximate composition of many common B&B fats. There is no one source for that data, so it takes some time, careful digging, and patient double checking. Soapcalc, for example, has a lot of oils in its database, but doesn't include fatty acids shorter than myristic or longer than linolenic. Working on stuff like that is helping me learn how the fatty acids contribute certain qualities to soap and that learning will lead me to .... who knows?
I love to teach, I'm a PhD engineer, and I'm definitely a geek. Does it show?
PS: Oh, and yes, I definitely also make soap.