Recommendation algorithm (and implementation) for finding similar items and users?

Actually that is one of the sweetspots of a graph database like Neo4j.

To determine similarity between users you can run cosine or pearson similarity (Found in Mahout and everywhere on the net really!) across the user vector. So your data representation should look something like.

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.