Two intersecting aspects form this book; tracking down the escaped animals from a Roman circus, and the romance between Flavia's father, a widowed sea-captain, and a mature lady from a well-to-do family, a romance which Flavia dreads will end in marriage.
The time is the winter after the eruption of Vesuvius, during the heady Saturnalia festival, today's Christmas. That's a lot to compress into one slim adventure.
While the focus is on kids under twelve, who have reasonable freedom to run around the port of Ostia, some mature themes are introduced. Romance between adults including parents, kid crushes on adults including a rock-star type crush, divorce, death, epidemic fevers (perhaps malaria), marriage, parental control, and a young woman behaving outside the gender stereotype.
Everyone is shown as being flawed here, except the helpful Jewish doctor and his family. All the Romans are conniving, bossy, dismissive of the feelings of others. Flavia is a flawed heroine, because she is growing up, and these are her role models. Nubia, a freed slave, also has an unrequited love, but she demonstrates her bravery while capturing the animals. The other exception would be Lupus, a mute boy formerly poor, who is growing into his talents.
The twelve tasks are incidental except as pointers to where information may be found, because little has to be done in the way of stable sweeping. They serve to demonstrate how Ostia was filled with murals, statues, temples, references to mythology. And of course, they teach young readers about Hercules.
There are so many twists that a reader too young will just keep going to see what happens next, without fully appreciating the background. Adults and readers from twelve up will get a great deal from the work.
I read a paperback. This is an unbiased review.