In a small used bookstore on a side street in Thessaloniki (I can't recall exactly where) I picked up a used copy of Sakis Papadimitriou's the "other" piano for 4 euro. Papadimitriou, a veteran jazz pianist and author in northern Greece, offers a diverse and visually stunning (black and white photographs by Aris Georgiou) description of ancillary techniques for the piano. In our workshops with composers at the Aristotle University, Jana Luksts and I used the other piano as a solid visual reference tool for students beginning to experiment with extended techniques on the instrument. Second to actual experimentation itself (and good recordings of hallmark works along with score study), the photography is just great enough on its own. I've included small excerpts of the book (and photos) below - in the future, with some more free time, I'll translate it into English.
Order a copy for yourself online at Ianos, 14 euro.