The most signficant of these, from our present perspective, has to be "I Was Born in the Country", in which he describes life growing up at Whitemill along with insights into rural life in general.
Known to most people simply as H.S. the remainder of his books reflect his love of the countryside and the joys of fishing. I am told that a couple of the fishing books are now recognised as classics in the genre.
Sadly, none of these books are available new. For second-hand editions, you might try the Advanced Book Exchange - a kind of clearing house for dealers in second-hand books all over the world. Give it a go - but keep your wallet locked up.
His known publications are: