The Night Eternal (Strain Trilogy #3) by Guillermo del Toro and Chuck Hogan--I don't really have a lot to say about this. I enjoyed the first book in this series, The Strain, as I thought it provided one of the more realistic (and, therefore, scary) explanations of vampires-as-virus theories that I'd ever read. Planes full of plague (read: vampires) land in major cities around the world and BOOM! Vampires spread through the population like a hot virus.
The second book, The Fall, I never even reviewed. I liked it, but not quite as much as the first one. The world has been consumed by new vampires (literally!), and one ancient vampire, The Master, is bent on world domination. Lots of plotting and scheming are involved as well as a secret vampire-y book bound in silver (because it is full of vampire secrets!). There are still some humans fighting the good fight, and if they can get the book, they might have a chance.
Now you are up to date for The Night Eternal. The book has been found, but The Master has gained a lot of control and most humans have either been turned into vampires or moved into food camps (a vamp's gotta eat!). The earth has been plunged into nuclear winter...or at least nuclear night--only a few hours of daylight every day--very convenient for the vamps, not so much for the humans. The only chance for humans to take back their planet is to destroy The Master and the only way to do that is to destroy his origin site and the only way to do that is to decode the secret vampire book. Of course, this part of the story was the suspenseful will-they-or-won't-they-make-it-in-time part, and it was OK. I felt like the dialogue was kind of clunky--it may have been the same in the previous books and I just don't remember, but here I really had a hard time with some of it. I also had a hard time with the characters' relationships. The first two books take place over the course of two weeks, and everybody is pretty close-knit, either through their previous relationships or just by virtue of the fact that they all came together as survivors. The last book takes place two years after The Fall, and the relationships have shifted. I suppose this is normal, but I just didn't quite buy the way everything seemed to have fallen out.
What I did like about this book was the vampire creation myth that is revealed in between bits of action. There is one vampire that is fighting on the side of the humans, and you get his backstory and, along with it, you find out where The Master came from, which I found pretty interesting. (Stephen King and I seem to disagree--his review is on the Amazon.com page, linked above.)
So, to sum up, I'd highly recommend The Strain, and if you're going to read that one, you might as well read the other two to see how it all ends.