Free six-volume physics textbook, intended for “ pupils, students, teachers and anybody curious about nature: the text is full of telling anecdotes, captivating riddles, unusual tables, astonishing photographs and beautiful films.”

“Entertaining and surprising on every page, the first five pdf files tell about

1. Sport, raindrops and animal life: mechanics, gravity and heat,
   
2. Moving empty space and the sky at night: relativity and the structure of the universe,
   
3. Lightning, lasers and nerves: electricity, optics, the brain, language and truth,
   
4. Colours and the quantum of change: quantum physics and light quanta.
   
5. Pleasure and the stars: biophysics, nuclear physics and radioactivity.
   

The sixth and last volume presents, in contrast to the previous ones, a research topic: it tells about the search for a final, unified theory of physics.

Prizes and rewards are offered for solving a number of challenges and for helping to improve the text.”

http://www.motionmountain.net/index.html

I have a large number of science books that I am prepared to give away free to a good home.

eg. Misner, Thorne and Wheeler “Gravitation”, paperback. Price new, $93.