4.5 stars, actually.
If the first book, Forgotten, introduced us to the fascinating bunch of young adults who were experimented on by the mysterious O'Brien research facility with just enough tantalizing detail to hint at why they are broken and unlike any other youth you have met, this second book in the series fills in the details.
Lots of details. We get cool glimpses of Lena and Flint's relationship as they were growing up in the Forbidden Hills. We get flashes of traumatic memories from Lena of what it was like in the facility, and we get a lot of Flint and Lena together (and there was much rejoicing.)
We also get the gang exploring their new powers, and then putting them into use as they return to O'Brien for any remaining lost children. No spoilers here, but the end of the book has Lena in a seminal moment of coming into her own power and confidence, as well as the addition of a few intriguing new members to the gang.
The story does start off a bit slow, and sometimes, despite Flint's sexiness, I wanted Lena to be so accepting of his overprotectiveness, but all in all it's a minor quibble of personal taste. Off to read the next one!