Classical Guitar Making
The first one is Classical Guitar Making by luthier John Bogdanovich. It's heavily illustrated with full color photography all through its 310 pages. The book is intended as a complete instruction manual for those who would like to build their very first classical guitar. Bogdanovich himself says in the preface that he wanted it to be the sort of book he would have wanted when he was starting out. It assumes that you have some woodworking background.
It is not an exhaustive manual as Bogdanovich wanted to focus on the build process. Readers would need to refer to other specialty books if they wish to explore related topics in greater depth (acoustics, the qualities of less conventional woods, and all that sort). This book impresses me however as more than adequate for the job and it is the best that I have seen to date.
Even if you have no plans to build a guitar, it might be a nice tome to add to your library so you can better understand the work that goes into the instrument. I doubles very nicely as a coffee-table book.
Engineering the Guitar
This is a somewhat small book even with its 264 pages and I thought it might be a light read when I picked it up at the library. Nothing could be further from the truth. They were certainly not kidding when they used the term engineering in the title.
I have not seen a more in-depth book that covers the acoustics, manufacturing, and structural performance analysis of the guitar than this one. If you did not get past calculus in high-school or in your first year of college, then large portions of this book will be inaccessible to you. Richard Mark French, its author, wrote this book for his students in mechanical engineering.
Two books are recommended to read alongside this one: The Physics of Musical Instruments
I am not entirely intimidated by this book but it is not something that I plan to read before bedtime. Two cups of coffee, a notepad and a well-sharpened pencil might best accompany it. If it's anything like my college class in advanced econometrics, then some ibuprofen tablets should also be kept handy.