Will Shortz was the NYT "puzzle master", a legend in the field, the guy carved quite a niche for himself, created his own college major by the courses he selected - logic, cryptography, etc.
There were always underlying riddles and themes running through the Sunday crossword. I bought a few of his NYT crossword books, loved doing them. I just wish they would have continued releasing editions for the e-ink Kindle, they released about five I think, I went through them, waited for additional releases... and they never came.
Monday puzzles were easy, got progressively more difficult as the week went on, until the Saturday ones were made by sadists for masochists. The Sunday edition was about Thursday-level difficulty, but four times larger, which was near my perfect balance of being maybe able to solve and feeling a real sense of accomplishment.