''Small Worlds: The Dynamics of Networks between Order and Randomness'', by D. J. Watts. ISBN 0-691-00541-9

The very core of understanding and using DistributedSystem''''''s. If you read one book, make it this one. It concerns how information passes from clusters of related participants. Consider the 'Kevin Bacon Game' or the 'SixDegreesOfSeparationTheory'. It's not a mathematical book but it is technical. You will get most out of it if you are familiar with basic networking, calculus, statistics, GraphTheory, basic programming, and QueueingTheory. 
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CategoryBook