One such book is 50 years of Porsche 912 by Jurgen Lewandowski.
A fact not known to me was that in 1965 Jim Clark drove a 912 through the Bruning Pass and thought that the 912 felt so safe and firmly attached to the road that he was quoted as saying " Finally a Porsche that stays under your backside" which was reported in a Swiss Motoring Journal.
Fine praise indeed from one of the top racing drivers of all time.
Mike