Take a look at https://cwiki.apache.org/confluence/display/MAHOUT/Books+Tutorials+and+Talks https://cwiki.apache.org/confluence/display/MAHOUT/Books+Tut... It

Take a look at https://cwiki.apache.org/confluence/display/MAHOUT/Books+Tutorials+and+Talks https://cwiki.apache.org/confluence/display/MAHOUT/Books+Tut... It covers more then just recommendation systems - but has some real gems.