Engine9

For beginners in aviation, highly recommend The Lore of Flight by John W. R. Taylor / Tre Tryckare, first published in 1974, and the most recent revised edition published in 1990 - easy to grasp, well-illustrated, and rather informative With respect to MS Flight Simulations, Microsoft Flight Simulator X for Pilots: Real World Training by Jeff Van West and Kevin Lane-Cummings is as good as it gets, and while it is written with FSX in mind, the underlying concepts and principles can be easily translated to the latest generation of MSFS; in fact per online discourse, the book still holds significant relevance and remains highly applicable, even to this day! Happy flights and safe landings!

As a tip, in avsim extended search, filling in the 'author' field with 'Craig Ritchie' yields a good collection of his TFS base AI models

Ebay is your best bet

Freeware, per https://web.archive.org/web/20181118000441/http://akesoft.es/index.php/downloads

https://library.avsim.net/extsearch?extended_search%5Bname%5D=777&extended_search%5Bfilename%5D=&extended_search%5Bauthor%5D=Ritchie&extended_search%5Bcategory%5D=38