Alan Cassidys book is quite technical about the standard aerobatic figures (loops rolls spins etc etc.). I don't know of one that is more technical, but I suspect Alan didn't put all he knows into the book as that would probably be too much detail for 95% of the readers.
Xaviers book is not really about the standard aerobatic figures. It is more about the gyroscopic figures such as Ruades, Cravats, Flat spins and knife edge spins. These are the sort of figures that are used in display flying. His book is quite technical, explaining how gyroscopics and aerodynamics control a figure.
So, get Alans book for classic aerobatics and Xaviers book for gyroscopic figures. Both have enough detail to get you in and out of trouble but I don't know where you go for more. I suspect its not written down because I can't think of many people who would want more detail. You may need to discuss with experts rather than reading about it.