<P> The Mortal Instruments is a series of six young adult fantasy novels written by Cassandra Clare, the last of which was published May 27, 2014 . The Mortal Instruments is chronologically the third series of a proposed five in The Shadowhunter Chronicles but it was the first one published . It follows Clary Fray (who interacts with a group of nephilim known as Shadowhunters) while also discovering her own half - angel heritage . The Shadowhunters protect the world of mundane people who are also called "mundies" from dark forces from beyond their world . </P> <P> The book series has become one of the most popular within the young adult genre of paranormal romance / urban fantasy, but Clare did not originally intend to write the series for teens . When she began writing City of Bones, she did not view it as a young adult work, but first and foremost as a fantasy novel, where the main characters just happened to be teenagers . When she was approached by a publisher interested in aging up her characters, she ultimately decided that she "wanted to tell a story about characters at that crucial life stage just between adolescence and adulthood, where your choices determine the kind of person you're going to be rather than reflecting who you already are ." The decision to launch her novels as Young Adult books has propelled Clare to the top of the Bestsellers list and has established The Shadowhunter Chronicles as some of the most popular works read by a largely young adult audience . </P> <Ol> <Li> City of Bones (published March 27, 2007) </Li> <Li> City of Ashes (published March 25, 2008) </Li> <Li> City of Glass (published March 23, 2009) </Li> <Li> City of Fallen Angels (published April 5, 2011) </Li> <Li> City of Lost Souls (published May 8, 2012) </Li> <Li> City of Heavenly Fire (published May 27, 2014) </Li> </Ol> <Li> City of Bones (published March 27, 2007) </Li>

What is the second book in the mortal instruments series