The format of The Twelve follows that of The Passage. There's another story from the Time Before, followed by a related tale from a century later. Bram Stoker's Dracula is mined for more ideas. We encounter another uniquely crafted colony of survivors.
I'm beginning to suspect Cronin has a bad case of dissociative identity disorder--there seem to be at least three distinct people contributing to his books. First is the Writer: as in the previous installment, the story is nicely detailed and the author seems to know plenty about whatever subject he happens to be writing: oil refinement, propaganda, navigation, whatever. Terrific world-building. Second is the Little Girl Who Loves Unicorns: she's behind the goofy story element in which a wild horse appears out of nowhere and spiritually bonds with an important character (the editor really should have gone after this bit with a chainsaw). Third is Michael Bay: he's responsible for the stupid climax in which lots of things blow up and good guys become unlikely bulletproof killing machines. The whole mess was clumsy and unnecessary. Cronin wrote a wonderfully tense scene earlier in the book involving a human-vs-drac cage match. He should have gone back to whatever place that chapter came from.
My feelings about The Twelve are really mixed. Sometimes I couldn't put it down; at other times it was a chore to pick it back up again. I was moved by the whole beginning-of-the-apocalypse opening involving the struggles of the early survivors, I loved the long detailed denouement, I loved many chapters in between. I hated the way dead characters kept popping back into play like Marvel superheroes (some made sense; others glaringly did not), I hated the way Cronin casually rewrote his vampire mythology to serve short-term plot needs, and I hated his reliance on coincidences to drive the story (yes, I recognize that not EVERYTHING that appeared to be coincidental actually was coincidental). Too many bits felt contrived.
Much like The Passage, this is not exactly a 3-star book; it's a 4.5-star book and a 1.5-star book mixed together. Given how good it sometimes is, I keep hoping for something amazing. I'll probably read book 3 with high hopes, and I'll probably be disappointed again.