Intro: para qué sirven los problemas de vida y muerte

To save others repeating the digging I just did:

The stack of books is the ten-book series 围棋从入门到九段 (weiqi from beginner to dan), a total of 10,000 problems. Currently these are $30+ each from Amazon. A taobao reseller like cssbuy looks to be about $5 each, although shipping costs will also be significant.

(There are many other sources of go problems. One list is: https://weiqi.soumyak4.in/posts/puzzles/ )