C. Manson
Publisher: Henry Holt and Company
Cited by:
Maze, by Christopher Manson. It wasn't the first treasure-hunt book, but I didn't have a copy of Kit Williams' Masquerade when that went big. Maze was less artful but more twisty and riddle-like, with some wonderfully sneaky mixing of clues into the physical environment of the House. Its puzzle was in three parts, and the first was tractable even by a young puzzle-solver. The other two parts were basically not solvable at all, it turns out. I suppose that's the magic ratio for hooking people.
-- Andrew Plotkin