Chapuis, Alfred and Edouard Gélis. Le Monde Des Automates: Etude Historique et Technique. 2nd ed. Geneva, Switzerland: Éditions Slatkine, 1984.
This work is widely regarded by the experts -- automata collectors, automata restorers, and automata book authors alike -- to be the most comprehensive work on the subject. This two volume set spans 720 pages and is probably the most technically detailed treatment of the subject. The book is in French, which may be a stumbling block for many readers, but it contains numerous photographs and mechanical drawings that would make it useful in any language. While this book is valuable in any condition and in either edition, be careful not to pay first edition (1928) prices for the 1984 reissue.
Here is the eBay listing showing the covers, title pages, and a few illustrations within the set of Le Monde des Automates.