If you like mysteries and history you will love The Thieves of Ostia by Caroline Lawrence.  Flavia Gemina, the daughter of a sea-captain lives in the port city of Ostia in the year 79 A.D.  She makes three new friends who help her solve the mystery of who is killing the dogs on her street.  A great book that introduces you to life in ancient Rome and to both Greek and Latin languages.  A great way to learn history.  This is the first book in the series of Roman Mysteries.  I recommend it for fourth graders and up both boys and girls will enjoy the adventures of these four kids.