Suggestions please.

Best for me is still Jess Pourret's "The Ferrari Legend - 250 GT Competition" . This book also covers the TDF and 250SWB and shows the development of the GTO.

Woody

The two absolutly indipensable:
Ferrari legend 250GT competition /Jess G Pourret 1977
Ferrari 250GTO / Keith Bluemel and Jess G Pourret 1998

There is my favourite, the Alan Lis GTO book (Haynes F862, ISBN 0-5429-839-8) from 1991 that is very insightful and has driver comments for 1962/63/64 headed 'Behind the wheel' plus some wonderful colour and b/w pics and of course Michael L. Schoen's highly rated THE COBRA-FERRARI WARS 1963-1965, which I think was self-published.

My copy is elsewhere just now so I can't quote year or any IBSN no., but you will have to find a used copy and it wont be cheap, good luck.

Cobra-Ferrari ars was republished in 2005, ISBN 0-925093-0-2, not too hard to find, I bought a spare copy at Road America in July for $80