The textbook from Motion Mountain:
The project aims to produce a simple, vivid and up-to-date introduction to modern physics, with emphasis on the fundamental ideas of motion. ‘Simple’ means that concepts are stressed more than formalism; ‘vivid’ means that the reader is continuously challenged; ‘up-to-date’ means that modern research and ideas about unification are included.
The text is free - under two conditions: that (1) you do not charge money to others for anything containing any part of the text; and (2) you send a feedback email to fb @ motion mountain . net (without the spaces) with your comments on the sections you looked at. In return, I will answer every email with questions or suggestions. For an email with good questions or suggestions you will be mentioned in the acknowledgments or receive a reward - or both.
I have a new version of the text online. Enjoy!
Christoph