I'm reading a new (to me) series: The Roman Mysteries by Caroline Lawrence. The first book, and the only one I've finished to date, is called The Thieves of Ostia. I found it while looking for children's fiction set in or around ancient Rome, of which there isn't much; and unfortunately this one at least would be too scary for Leo, if not for me. It's set in Ostia, the port of Rome, 79 AD (so far so good), and features four unlikely friends: a sea captain's daughter Flavia, her new neighbor Jonathan, the slave girl Nubia, and the mute beggar boy Lupus. Together they search for whoever is killing the neighborhood dogs. The mystery is good; but the real appeal (again, for me) is the description of Roman life.
The second book in the series is The Secrets of Vesuvius. In this one, the four friends are spending the summer with Flavia's uncle near Pompeii. There they race to solve a riddle that may lead them to great treasure, and then to survive the volcanic eruption that ultimately buries the city. I have some hope that this one will not be too scary to read to Leo; solving a riddle seems much less dangerous than catching a dog-killer. But this is a kid who who won't read the Magic Tree House books by Mary Pope Osborne (which is fine) because Jack and Annie are always putting themselves in danger, no matter that they obviously come out of it okay: there are 38 books in that series to date! The Roman Mysteries will total 17, of which 14 are already available: I better get reading.