I've been reading a lot of
David Wellington lately.
Most of his books were originally published as free web serials, and are still available in that format at the link above.
Personally, I'm enthralled with his vampire series that starts with 13 bullets. Later entries (99 coffins, Vampire Zero, and 23 hours) are available as pbooks. (ETA: If you're interested in this series
DON'T look up or read the description for Vampire Zero until after you've finished 99 coffins. It's got a major spoiler.)
I also thought Frostbite was a great take on werewolf mythology. That one is due out as a pbook later this year.
My wife liked the Zombie trilogy (Monster Island, Monster Nation, and Monster Planet) well enough to read straight through. I'm not as big into zombies, but I'll probably pick them back up eventually.
Incidentally, I’d like to try turning the web serials into ebooks so I can go back and read them easily once my reader arrives. Can anyone suggest a faster method than copying and pasting 60 chapters individually.