96 pp, ill, 2010, Glashütte: Lange & Söhne Ten sections: Grande complication (24 pages, where perfect craftsmanship is combined with the beauty of an idea - a gallery); What is “irreplaceable” worth? (2 pages, an interview with auctioneer Stefan Muser about the value of the 42500 pocket watch); Fantastically rich (36 pages, restoration of the 42500 - timeline of an adventure); Anatomy of a treasure (2 pages, a journey into the inner workings of the movement); The functioning of the perpetual calendar (2 pages); The functioning of the chronograph (6 pages); The functioning of the striking mechanism (8 pages pages); Great art (2 pages, the grande complication in the history of watchmaking); Devine handiwork (10 pages, about engravings by A. Lange & Söhne and the designs of Professor Graff); and A lot of money (1 page, the value of money in 1902). The grande complication, serial number 42500, was made in 1902. It includes a perpetual calendar with moon phases, split seconds chronograph (with jumping one-fifth seconds and 60-minute displays, and separate barrel), quarter-hour striking (also with a separate barrel) and minute repeater. The watch was then “lost” to reappear in 2001, rusty, incomplete and partially destroyed. Lange then invested some 5000 hours over 5 years to restore it. The book begins with an extensive and excellent photo gallery showing the restored watch. Some concrete information is given in the captions, some of which will only make sense to the knowledgeable reader. This is followed by the predictable comments of an auctioneer on the probable value of the watch. In the third section (“Fantastically rich”) Jan Sliva provides a history of how the watch came to Lange in 2001, the problems and questions raised when considering restoration, his experiences disassembling the movement, and how components were restored or remade. A few sentences are obscure, as when he refers to the “dragging counter-hand wheel” without explaining what it is, and there are a couple of annoying and unnecessary errors, such as describing a mainspring as a gong. But it is a fascinating account. (Other strange terminology appears elsewhere in the book, and I presume this results from using a translator not sufficiently familiar with horology, unfortunately too common.) The following technical description of the perpetual calendar is quite good. However, that of the chronograph is much more difficult to understand. In part this is because photographs of the mechanism are used whereas drawings showing the various positions of the pieces and their interactions are needed. The striking and repeater mechanisms are, naturally, even more difficult to comprehend. This part of the book is weak. It would have been better to either gloss over the mechanisms or devote many more pages to them and so explain them more fully. The remaining three short sections are a very brief history of complications (too superficial), an interview with Lange’s head engraver about Graff, the probable designer of the case (interesting) and a comparison of what could be bought for 5,600 marks in 1902 (trivia). The book is worth reading for the description of the restoration, and some information on the mechanisms can be gleaned from the technical notes. [Remark] At the time of writing I found no information on what has happened to the watch; certainly it has not been sold at auction. So who now owns it? And who paid for the restoration?