Nicola knows she will die. She wants to be involved in the process and help deliver herself to her fate. She thinks it will be either Keith or Guy to kill her, and she masterfully attempts to make each of them fall in love with her, thinking she will be killed somehow in relation to this. On the sidelines is Samson, a dying author who is writing about all three of them, and has interactions with them, like little sideline interviews, and his parts don't make much sense and make you confused.
The characters are all stereotypes: Nicola Six, Keith Talent, Guy Clinch, and Samson Young. Amis doesn't try to cover this fact up at all, and it is assumed like a contractual agreement between the reader and Amis that his characters are going to act as stereotypical as possible, and therefore you can't get him on that part, because it's out in the open, but you need to look deeper.
In looking deeper, there isn't much to be found. I would say that London Fields is a book about love. It's not romantic love by far. It's a weird, twisted, sadistic love that each of the characters represent. However, I don't think Amis every goes deep enough. He kept scratching the surface.
The only character that I think Amis got right was Guy Clinch. I don't think Nicola, Keith, and Samson were extreme enough. Everyone, except Guy, seemed like stupid, wooden puppets that Amis was gleefully manipulating, thinking he is getting that characterization perfect, when in fact I get the impression Amis has never met a femme fatale or a lower class person once in his life. All very one-dimensional.
I found the lower class to be written in an unbelievable manner. It's hard to say that for this story since it is about stereotypes and therefore how believable is anything going to be. However, we never really see the true dirt of the working class. Amis hints at a few things every so slightly. It came off as rather boring to me.
I got the impression when he was writing this story, he put down every single cool, interesting thought he ever had in his brain. Now, this makes for some great philosophical consideration, and there are some wonderfully, written portions of prose that are truly excellent. But, where was the cohesion? Where in all these random thoughts does it all come together? It doesn't.
Towards the end I was really drawn in because I wanted to know what happened. The ending was anti-climatic. Why have stereotpyical characters if it doesn't lead to anything?