My paper The Structure of the Multiverse ([quant-ph/0104033] The Structure of the Multiverse
, which appeared in Proceedings of the Royal Society A458 2028 2911-23 (2002), explains how the structure of the multiverse – and in particular, the way in which some parts of it consist, to a good approximation, of parallel universes – is determined by the way in which information flows in it. But before that, you should read:
Information Flow in Entangled Quantum Systems by myself and Patrick Hayden, which appeared in Proceedings of the Royal Society A456, 1759-1774 (2000), explains how, despite conventional wisdom and a great deal of futile work by many researchers in the foundations of quantum theory, there are no non-local effects of any kind, detectable or undetectable, in quantum physics.
Quantum Theory of Probability and Decisions, which appeared in Proceedings of the Royal Society A455, 3129-3197 (1999), is about what probability really is, and how the quantum theory of a deterministic multiverse, without any probabilistic assumptions, makes probabilistic predictions.
See also the following papers by David Wallace:
Everettian Rationality: defending Deutsch's approach to probability in the Everett interpretation
Quantum Probability from Subjective Likelihood: improving on Deutsch's proof of the probability rule
And other papers on his web site.
Michael Clive Price's FAQ on the Everett Interpretation. I do not necessarily endorse everything in it, but it does indeed answer many frequently asked questions correctly and is a good non-technical introduction to what the theory is about.
This draft biography of Hugh Everett by Eugene B. Shikhovtsev contains many fascinating details about Everett's personal and intellectual life. For instance, there is the story of how Everett, aged 12, wrote to Einstein, and what Einstein replied