The 4 star rating reflects the book's applicability to a d20 game "out of the box." This is not a stand- alone d20 super powers add-on. Power costs are listed as low, medium or high, and rage and duration are given with similar descriptors, so you'll need to have another OGL supers system on hand that accounts for power point allocation, or devise your own. Rules hungry players may also take issue with what a given GM qualifies as low, medium, etc. That being said, the write-ups themselves are detailed and innovative. For you crunch-lovers out there, new feats are also included.

Now, if your not using this book in a d20 game, raise the rating to 5 stars because the above mentioned power cost descriptors that could be so problematic to an OGL game lend themselves to more narrative, stat-lite games like Fate [ a low cost power functions as a Stunt mapping to one or more Skills that doesn't require the expenditure of a fate point to activate; a medium would require 1, a high 2--my rough conversion for illustration purposes].

This product also has high production values--nice, appropriate art, readable text, etc.