Just to add few words to this conversation...

I think that this book idea is good and most likely I would've bought it myself.

My only suggestion is that you explain clearly OOP concepts, inheritance and all the specifics to Pascal language. From what I've seen on Afterwarp.Net, many people still lack information on how to design classes well (for instance, a word "reintroduce" or "dynamic" is pretty unknown among many Pascal programmers).

If you guys need any assistance with writing some blocks about using inline assembly or even MMX/SSE specifics (well, if you decide to add this to optimization section) - you know where to find me.

Also, I agree that sticking to specific API (not only DelphiX, but even Direct3D or OpenGL) is not a very good idea. The specific API is choosen to fit the needs of market and project requirements, so by explaining an API like OpenGL you almost bind the reader to that API. However, some basic information about various APIs and links to some development and download sites would be handy.

Finally, what I would suggest is excluding DelphiX not only from the book, but also from any conversations. It's very limited in the concept and rather outdated.