Dates: Book One Oct 2009; Book Two Nov 2010; Book Three Aug 2011; Book Four Feb 2012; Book Five Jun 2012; Book Six Feb 2013; Book Seven Sep 2013; Book Eight Feb 2014; Book Nine Oct 2014; Book Ten May 2015; Book Eleven Nov 2015; Book Twelve May 2016; Book Thirteen Sep 2016; Book Fourteen Apr 2017; Book Fifteen Nov 2017 Hardcover