Pros:

-Recreates elements from the book, could feel like you're there at times.
-Definitely Challenging, flooding of zombies with just pistols can be a pain, but was enjoyable.

Cons:

-A lot of empty space, felt too open for a L4D map.
-Too few spots with a medium amount of zombies, felt like      there were 5 zombies, or 500.
-Can be overwhelming if playing with bots
-Narration, while creative, was too quiet, and didn't add anything to the enjoyability of the storyline.

Conclusion:

Definitely worth a playthrough if you've read the books, otherwise, I'd pass.

Author seems to have a talent for developing campaigns, and I'd gladly love to play another.