Here are my thoughts on why I give a certain adventure module a certain "rating". The ratings are absolutely subjective and qualitative, and I'd recommend you (the reader) ignore them - if an adventure sounds interesting, get it anyway, and if it's not interesting sounding, who cares how I rated it? The scoring is really there just to help me calibrate reviews. I'm hoping to do one review per week.
This module turns a genre on its head, breaks creative new ground, and otherwise stands above the crowd.
Breaks creative new ground or demonstrates a level of effort far beyond what I'd do for the home game.
3 Good Effort
Worth buying! Either a polished home brew or the start of something creative and new (but unpolished).
2 Home Brew
This adventure is something I'd expect a creative DM could home brew on their own; you're not missing anything.
1 I Want My Money Back
I try to be risk averse not to buy modules that could be in this category, but I suppose it could happen.