Cypher is the query language for Neo4j graph databases. In fact, in my thesis about user profiling, i use cypher and i am plannig to write a post about cypher after publishing my system for evaluation..
http://www.neo4j.org/learn/cypher provides good information about cypher.
Moreover, i am planning to review the book on http://bit.ly/QZ5Alw ..
i recommend to try graph databases and cypher if you are dealing with connected-data problems..