A good, solid T3 entry. It's fun, witty, and entertaining -- but could use a massive editorial pass.
The back-and-forth bickering of the party's two sage allies provides a comedic backdrop as needed (I kept turning the 'like an old married couple' into 'these guys are in a relationship' and the parties loved it), while their absent-minded professorism keeps the party on edge. The characterization of the lich had people laughing and enjoying themselves at his expense.
The mod's author actually pays attention to the general structure of a 5E adventuring day, with a series of encounters, rather than trying to throw one or two mega encounters at players. He also includes built-in short rests to help nudge the short-rest characters into line.
1 on 1 combats can be fun. The entire party getting stuck in a set of 1 on 1 combats, not so much. I saw combat oriented characters blast their opponent with ease, while social, support, and similar characters struggled to stay alive. That section could also use an editorial pass to clear up it's instructions, I'm still not sure if I quite ran it 'right'.
As for the Bibliomancer, I had to use the sages to shortcut this 'puzzle' -- because the answer wasn't included. If you're gonna include a puzzle, give the DM the answer. This entire section could do with a rewrite, to help clarify things. (What 'flaw' did the bibliomancer have? The sages agree there is one mentioned in the previous section, but there's no flaw mentioned there!)
Psycic Scream with a DC 20 save is a GREAT opener. Unfortunately for us, it's stun effect doesn't go away until a character passes the save. That means that not only is it possible to lock players out of the entire final fight (which isn't that much fun for them), if a character has a negative int score (say, barbarian?), they can never save. Never, ever, ever. Evena nat 20 doesn't save them, since you can't 'crit' a saving throw. We had people walk away with permanently stunned characters that we had to handwave away and let the locals heal in the healing room.
[4 of 5 Stars!]