Assuming you speak German, and have a weakness for the small Honda roadsters of the 1960s, the small Kindle booklet certainly delivers valuable information. The author starts with his own experience in buying one second hand, the travails of keeping it on the road at a time when the dealer network and the parts situation left a lot to be desired, and then gets to the inevitable sale. Following the own experience is a chapter on the history of the car (let's call it abridged), with a view on how it got to Germany and how it sold there, too. Following that come technical specs of the car, together with its predecessors S360, S500 and S600, as well as its spiritual successor (S2000).
The penultimate chapter is probably the most valuable one - namely about buying and restoring an S800 and what one needs to consider, when embarking on the journey. The book comes with practical guidelines on which parts are hard to source / expensive (and should therefore function on a car you buy), some price guidance and general advice on whether to go for it. Helpfully, he also provides some basic information on the main competitors of the time (Triumph Spitfire, Austin Healey Sprite, Fiat 850, NSU Wankel Spyder, VW Karmann Ghia...).
Overall a good little book, with some nice photographs (unique, as the author's own) and solid information for a potential owner of an S800 - something I would definitely recommend if you plan going down that route and speak German.