[jluetjen]

Here are my fave's that I always seem to be re-reading:

The Porsche Book by "Lothar Boschen and Jurgen Barth" Details about every Porsche made. A couple of questionable facts, but overall better then most books.

Dittoearlier posts: 911 R-RS-RSR as well as 930 to 935. Both by Starkey.

Any "Brooklands" books on 911's. They contain copies of R&T, MT, Motor, and other contemporary magazine articles on the cars.

Anything (Everything?!) by Carroll Smith, especially the "To Win" series. "Tune to Win" is the most applicable to the average ethusiast as well as "Drive to Win".

Think to Win by Don Alexander: A great book about competition driving.

Here are a few not-obvious (ie: Not specific to Porsches) books which are excellent:

Four-Stroke Performance Tuning by A. Graham Bell. He goes through the engine system by system and describes how they are modified for racing.

How to Build Horsepower (Vol 1) by David Vizard.

SpeedPro Series Books: How to Modify and Tune Cylinder Heads" by Burgess and Gollan and "How to Choose Camshafts and Time Them for Maximum Power" by Des Hammill. BTW; don't waste your time with "How to build and Modify Cylinder Heads, Camshafts and Valvetrains" by Watson. The title is similar by the contents are not!

Finally; Skip Barber also has a video that contains a lot of the stuff that they teach in the 3 day classes.

PS: A fairly recent release that I really like is Peter Morgan's "Porsche 917 - The Winning Formula". It is a really good telling of the 917 story. It focuses more on the personalities and events but also covers adequate technical detail. It also has a lot of great photos.