Sifu used to have three bookcases filled with tai chi, tao, zen, martial arts and spirituality books. The bookcases were six feet tall and about four feet wide. There were a lot of books.
Every time we moved house he'd have to box them up. Eventually he gave away two bookcases worth in order to make it easier when moving house.
Occasionally Sifu thinks about replacing one of the books he used to own and looks it up on Amazon only to find that it is now out of print and a new copy will cost £50 - £100. I've found books on his remaining bookshelves that are worth hundreds of pounds. No idea why they are worth so much.