Not surprisingly, being a motor sport junkie, my favourite books have a competition focus. Anything written by Evan Green is gold, particularly A Bootful of Right Arms, but others I've read many times are Frank Gardner's Racing Driver's Manual (pub.1973) and all the F1 books written by Niki Lauda covering his entire F1 career. Some aspects have certainly dated since these were published, but the words and period images remain fresh and entertaining as are the cars and technology of those times. I can thoroughly recommend these books.