 Barrowman 's first published work of original fiction was a Torchwood comic strip , titled Captain Jack and the Selkie , co @-@ written with sister Carole . Commenting on the characterisation of Jack Harkness in the comic strip Barrowman states : " We ’ d already agreed to tell a story that showed a side of Jack and a part of his history that hadn ’ t been explored too much in other media . I wanted to give fans something original about Jack . " Barrowman 's début fantasy novel titled Hollow Earth , co @-@ written with his sister Carole , was published in the United Kingdom on 2 February 2012 by Buster Books . The novel is about twins Matt and Emily ( " Em " ) Calder who share an ability that allows them to make artwork come to life , due to their powerful imaginations . Their ability is sought after by antagonists who wish to use it to breach Hollow Earth — a realm in which all demons and monsters are trapped . Two sequels from the same team concerning Hollow Earth followed - The Bone Quill ( 2013 ) and The Book of Beasts ( 2014 ) - and <unk> ( 2016 ) , the first in a new series ( the " Orion Chronicles " ) featuring the same twins , as well as a separate novel Torchwood : Exodus Code ( 2013 ) . 
