Books on piano technique and interpretation?
I've read a few things from the Golandsky institute that were not really helpful, as well as a book by Tobias Matthay. I'm coming around to the conclusion that it's impossible to write about technique in a useful way (beyond platitudes about relaxation, etc.) and that getting in-person lessons with a good teacher is the only way to progress here.
(Actually, there are some helpful YouTube channels, but also a lot of low-quality content there. Let me mention this little-known channel by a working pianist as exemplary; the link is to a video representative of his philosophy on playing.)
There's also the infamous book by Chang, which is freely available. There's a lot of good advice there, but also some very questionable statements (playing piano while sick causes brain damage?) and perhaps an overemphasis on memorization and hand memory as opposed to sight-reading. In terms of practice advice, I found this short blog post very sensible; essentially it's a summary of Chang's book with the bad parts taken out.
However, regarding interpretation and learning about new works, books on specific composers have been very useful to me. Let me mention David Schulenberg's book on interpreting Bach's keyboard works and the The Alexander Scriabin Companion by Ballard, Bengtson, and Young as particular standouts, though of course there are many others.