The Day of the Triffids is one of the most famous and one of my favourites. It's just one of those novels that sticks with you forever. I love how it cleverly shifts between survival from each other and survival from the triffids. 28 Days Later... was in part based on it, making that one of my favourite films.
I Am Legend is another cracker. Shorter and more intense than TDOTT, the focus on the protagonist going mad is brilliant and the ending is one of my favourite endings of any novel. If you've only seen the Will Smith film, which butchered the ending, read the novel, if just for that ending.
Additionally in my bookcase alone I've got:
The gritty, ultra-realistic yet beautiful The Road.
The painfully boring The Pesthouse.
The entrancing The Chrysalids.
The stunningly-written, if heavy-going, Riddley Walker.
The paranoia-drenched The Penultimate Truth.
The uniquely satisfying A Canticle for Leibowitz.
But if there was one post-apocalyptic novel that really grabbed me by the collar and kicked me in the groin, it was The Death of Grass by Samuel Youd, writing under the pen name of John Christopher.
A simple concept; a virus that attacks rice crops and all forms of grass, spreads across the world bringing famine and eventually causing the world to descend into chaos. The story follows the narrator and family trying to make their way from London to his brother's farm in Westmorland.
It's an incredibly bleak and disturbing novel. The characters descend into moments of barbarism comparable with The Lord of the Flies and it's all too convincing. I only wish I could have been around to read it on publication in 1956, before I'd become desensitised to the violence of films and novels.
I can't help myself but talk about one of these barbaric moments in the novel, so stop reading if you like post-apocalyptic fiction, because I'd really recommend The Death of Grass.
***SPOILERS***One such example of the brutality of this novel, is when the narrator and his family approach a house about a third of the way through. They knock on the door and the owner and his wife warn them away with shotguns. The narrator and friends then murder this innocent family simply to grab some supplies under the belief that, "it was them or us." This violence is emphasised by the fact that the main characters are all likeable, 'nice' people. This shock value continues right up until a truly unforgettable and disturbing conclusion, which I won't spoil here. Just read it.