I have just finished "Jaguar the Prototype racers":
Good book if you are a Jaguar fan, as it covers all chassis numbers and gives a good account on Jaguar's charge in group C and then IMSA. Found it a bit too little technical but I guess it will please most people. Lots of pictures as well.
My next book in this line of books is Sauber C9 Return of the Silver Arrows: