This book is the second in the Vampire trilogy jointly written by Guillermo Del Toro and Chuck Hogan. The trilogy began with 'The Strain' which followed the aftermath of a 'terrorist' style event involving a plane full of dead passengers landing in New York. The main storyline follows Dr Eph Goodweather, an epidemiologist investigating the biological threat, with the help of an ancient vampire hunter named Abraham Setrakian, minor characters include Eph's son Zack, and a rock star turned vampire who was on the plane when it landed. The villain in the series is 'The Master,' the vampire who orchestrates the invasion of vampires in New York city, with the help of the millionaire Eldrich Palmer.
These characters are introduced in 'The Strain,' and continue to evolve in 'The Fall' with each character becoming more rounded with detailed back stories and evident reasons behind their actions.
In relation to the main storyline, I have to admit that I read first book so long ago that I had to try really hard to keep up with the beginning of The Fall, I guess this is the problem you face in waiting so long for the second book to come out. The book was good at bringing me up to speed with events occurring in real time and with flashbacks to the characters' past, and solutions from situations in the first book.
The overlying theme in 'The Fall' is the Master creating Armageddon by over-running the city with new born vampires whilst wiping out the original ancient vampires. Inspired by Chernobyl, The Master causes nuclear disasters across the world to cause an environmental nightmare, blocking out the sun and allowing vampires to attack during the day.
The book reminded me of other well known trilogies (star wars, lord of the rings etc) as it does not seem to have a happy wrapped up ending, the bad guys rule the day, and it leaves you thinking 'how are they going to get out of this?' As it is created by a well know horror/ fantasy director it definitely reads like a film, and the scenes have a straight to cinema feel. I assume that they will begin making 'The Strain' well before the 3rd book finally comes out.

If you are looking for a good horror storyline, that has interesting characters and great insights into the human race dealing with fantasy/ natural disaster then you will not be disappointed with this series. It is gripping and it is very well written (as you would expect from 2 authors). In the face of vampire over saturation these days, it really is an original storyline, and it does not bother about tacky romances or old wives tales like garlic and crosses.
It leaves you hoping that they won't take too long to write book #3. My advice is read both books together so the story is fresh in your mind.
If you really dont have the time to read 2 quite long books, im sure the films will be out soon!