For Zombies i would recommend David Moodys Autumn books, these were the first zombie books i read and ive been pretty much hooked to the gener ever since, but never seem to find any books quite as good as his.
None zombie books are:
I just finished Old man and the Wasteland - only 77p on amazon kindle. Very good book.
Swan song i have yet to read but i have heard nothing but good things.
Roadside picnic is kind of post apocalyptic and a very good read, as is the Stalker book im reading at the moment, Southern Comfort.
Definatally Day of the Triffids.
Didnt enjoy War of the Worlds very much, but it was still a fun read.