Does anyone know any good isometric engine, that can be customized easily, and that includes lots of comments and explanations?

http://www.multimania.com/hatti/MrY/isoxeng.html
This is the homepage of the Isometrix engine by Yannis Deliyannis,the best you could find out there,with fully commented c++ code and a compiled example.You will also find in this page links to other isometric engines on the web.
Voodoo4