I reently started learning programmming. I decided to start with web programming. I covered XHTML and CSS, and am learning PHP and MySQL along with JavaScript. I plan to move on to more advanced stuff like AJAX and Ruby on Rails.

But I wish to start learning desktop programming as well and I'll either C++, Java, or Ruby. Which one is the best one to start learning?

And I am also looking for a book that can give me a theoretical introduction to programming that is not limited to a single language. Something that explains how programming languages work and what high and low level languages are, and how the computer hardware understands the language and stuff like that. Any suggestions?

I started programming using C++, nothing but object oriented command line stuff. It's actualy the best to start making programs without a GUI because you can focus on the basis of programming.
I'd also suggest that if you learn a programmling language, to choose one that is object oriented because most common used languages are (you'll also find most information about these languages).

If you like some challenge, try Java, I realy like the language, it's not that simple to learn, but very advanced and you can also use it to create programs for your mobile phone . Another language I suggest is C#, I've seen friends creating nice programs with it .