I write about the classic FIAT 124 Spider (1966-1985) and maintain a public library of information on classic FIAT automobiles sold in North America.
Maintaining the Italian Roadster - new edition!
Originally published in 2015 the new 3rd edition was released in December of 2018. It is available in color and black and white, softcover, from Amazon worldwide:
Note: If you buy the print version Amazon will give you a Kindle version. I don't recommend the Kindle version unless it is free - the book has yet to be optimized for the format.
FIAT 124 Spider Engine Maintenance and Modification
Originally published in 1997 and revised several times since, this could be called a home mechanic's guide to understanding the FIAT twin cam, improving reliability, performing tune ups, and making modest performance increases through stock parts.
This library is of documentation I personally maintain and is generally only for the classic 124 series. The most complete classic FIAT documentation set on the web is in the forum library on mirafiori.com - register (free) to gain access.