I'd only play this adventure as a precursor to the next adventure. It's not bad but it's just kinda average by itself. The introduction of the flayer is memorable but otherwise there isn't actually much content here. You as the DM have to design/make interesting underdark content.

I was not a fan of this product.

Essentially, this module is three encounters - a roleplay encounter that isn't very well-defined (as in, the NPC doesn't really have much of a personality detailed), and two combat encounters that really don't offer much. As in, there's a mind-flayer, but the encounter in which the flayer appears doesn't really do much to accentuate the flayer's strengths.

There's little advice on how to run the adventure if things go awry (not that there's much time for this to happen - there is, after all, only a handful of encounters).

And so many statblocks! SO MANY STATBLOCKS. Every monster from the monster manual has its own statblock here - which makes the whole thing seem bigger than it actually is. Even the random encounter has a statblock for every monster that could potentially appear. It reminds me of padding my papers back in college.

Final verdict: you can find better at the same price point. This is a hard pass.

This is a short, sweet, and simple adventure, designed to be inserted into an existing campaign or used as a one-shot. Several hooks are provided for the DM to bring the characters into the events of the story and there are enough twists to keep the players engaged and guessing until the true villain is revealed. A robust conclusion section offers a few potential places that the story can go after resolution, and a follow-up adventure is advertised in the back of the book.

Very well executed. HIGHLY RECOMMENDED!