Bought this yesterday, put the first two puzzles in my game today. The others looks good and not repetitive.
I can tell from the mention of 30th and 36th level casters that the author has "Master"ed the game. Some anachronisms from older editions remain, like Stone to Flesh, but they're all easy to work with. One works requires knowledge of spell components that fortunately did stick around to the newest edition.
There's one puzzle with 12 keys, 7 are normal keys, but I can only identify three that aren't normal. I'm not going to introduce a puzzle I can't solve myself.
But I've already gotten my money's worth. Like I said, lots of ideas, and the puzzles aren't too difficult mostly. (You want your players to feel they're smart, not to feel you're smart).
I would note that it's good to give puzzles like these while there are still places to explore, so the game doesn't grind to a half while the players who love puzzles work on it. Don't make a puzzle the only way to go with not side treks.
[5 of 5 Stars!]