Oh dear. After being absolutely blown away by The Passage, I immediately launched into The Twelve, only to become more and more disillusioned as time went on. By the end I was speed reading, skipping whole sections just to get it over with.
Where The Passage was bleak, and unremitting with peril round every corner and well-rounded characters dropping like flies in a gut-wrenching manner, The Twelve is full of convenient escapes, a total lack of threat, characters miraculously surviving impossible situations, returning from the dead etc etc. It turns into a pointless and tedious action adventure, with no suspense as all the main characters by now seem to be completely impervious to any real threat. Where the outside world was a dark and dangerous place before, where the slightest contact meant instant death in all likelihood, now it is essentially a safari. At the end, it really was just a bunch of stuff that happened, with no emotional weight whatsoever.
Its really, truly best just to read The Passage and leave the story there.