On Piano Playing: Motion, Sound, and Expression by György Sandör
I am about 20 pages in and I'm captivated. This is the first piano technique book so well written the I cannot put it down.
The path that led me to this book and to György Sandör is also an interesting one. @Seeker has been helping me with technique. One of the exercises he gave me is from Béla Bartók's Mikrokosmos Book 1. I've only heard of Bartók's name but know nothing else of him. So I did some searching about the composer, found some wonderful performance of his Romanian Dances, then a forum discussion about Mikrokosmos being an excellent "method book without instructions". In that discussion thread someone mentioned the book by György Sandör, who studied with Bartök for four years. That lead to the finding of this fascinating interview of Sandör by Bruce Duffie. Sandör is a prolific concert pianist and performed into his nineties. He was mis-characterized as Bartök and Liszt specialist for being Hungarian, but from I've learned he really is a great all-around pianist of the highest caliber.
Sandör's book is out of print, thus quite expensive. But if you google, you can find PDF versions for free.