Luckily, this is not the case with The Twelve. In fact, Cronin has become a better writer than he was when he created The Passage, the first book in this series.
The Passage was a great example of world building that got hampered by one of the most clunky reboots in popular literature. But, it did have great characters and a great premise so was fun to read.
The Twelve, on the other hand, avoids the reboot problem, fleshes out a more interesting story and lets the actions of the characters continue the world building - which makes for a much better read.
At the end of the day this is what a modern vampire story should be. It's scary in a way that Stephen King hasn't been in years and it doesn't romanticize the vampires.
Instead it gives a series of incredibly dark events involving characters we care about, even though we know they are doomed.
It has a bit of G.R.R. Martin Syndrome - in that it seems to give us more characters than we could possibly follow, but simplifies things by killing them off on a regular basis.
The result is a tight, terrifying interesting book where anyone can die at anytime all living in a world we really care about.
It's awesome and awful and beautiful and horrifying all at once - which is how it should be.