A couple of oldies from me:
Behind The Scenes of Motor Racing by Ken Gregory who was Stirling Moss' manager during his racing years.
Milestones in a Motoring Life by Dudley Noble. Charting his involvement with the growth of the British motoring industry including several speed/reliability trials to showcase the motor car as a reliable form of transport.
I must find the time to re-read them myself!
[Also +1 on Backfire by Alan Clark]