One thing I love about manga is the way there is invariably a different angle on a familiar type of fiction.  I read a lot of mysteries, but how many of them are set in modern Japan, tell their story pictorially or look at the genre in this atypical way?  This is a story about being in the shadow of an older sibling and getting the chance to rescue them, and complete a task they were unable to.  It is also a teasing detective story which manages, bloodlessly, to conjure up some interesting murders (including a locked room one) and their solutions.  Only each solution gets the detectives deeper into the mystery rather than solving it, leaving the reader with a good cliffhanger ending.  In short, although the protagonists of the novel are young, it is far too entertaining to limit the readership to teenagers!  I look forward to book two, and getting nearer to solving the mystery.