The title says pretty much all. I'm trying to use neo4j-reco by GraphAware on top of neo4j-1.9. However, I don't know if it is possible at this time.
No, the neo4j-reco has been built starting from Neo4j 2.1.5, see here : http://mvnrepository.com/artifact/com.graphaware.neo4j/recommendation-engine
And some methods use the Neo4j 2.0+ API.
In the meantime, we can just recommend you to upgrade to Neo4j 2.2