Free, at least today, for Kindle US (at least)
http://www.amazon.com/Dead-Kill-Stor.../dp/B003ATPQCK
Dead Men Kill by L. Ron Hubbard
L. Ron Hubbard is best known today as the founder of Scientology, but started as a popular pulp fiction writer.
This one is a 1934 detective novel (short by modern standards) involving zombies. One of the reviews mentions that it is far from Hubbard's best pulp fiction writing, so be willing to give another book a try if you think it's got some merit. But hey, it's got zombies!
I'm going to admit that I don't remember reading any L. Ron Hubbard, so I guess I'll give it a try.
KentE