The Red Scrolls of Magic by Cassandra Clare and Wesley Chu

Alec and Magnus are on a romantic European vacation when Magnus' past comes knocking.  It seems that at some point Magnus founded a cult and doesn't even remember it.  Now that cult is trying to raise a greater demon.  Alec and Magnus must stop them before the other Shadowhunters find out.

This is the first in a new Shadowhunter series by Cassandra Clare and Wesley Chu -- The Eldest Curses.  It focuses on the adventures of Alec Lightwood and Magnus Bane.  It was great to discover their romance as it developed.  It was also interesting to discover more of Magnus' past.  I would recommend this to anyone who enjoyed the previous Shadowhunter series.