The key to remember in this purchase data is that the major booksellers show just the most frequent links between books. They show just the TOP 5 'also bought books' -- these are the strongest ties in the network.

People like you, eclectic readers, apparently don't make the cutoff. If more people were like you then we would see something akin to a random network as opposed to the highly clustered network we do see. Frankly, I wish more people had the diverse collection of reading material you have. Unfortunately the data tells us that most people choose to read highly similar material.

Valdis