Most Comprehensive Chemistry Book(s)?
For the inorganic chemistry I recommend Holleman-Wiberg's text, also exists in english. It is reasonably readable and very thick and contains a lot. 
Holleman-Wiberg's Inorganic Chemistry. If you prefer, the original is in German and updated very often.

For the organic chemistry, besides being thick also very nicely readable,  Organic Chemistry by Clayden, Greeves and Warren 

Besides that, you would probably need some nice general chemistry book, but I have no good personal experience in this area.