Hannibal, Enemy of Rome, Ben Kane.
It starts just before the 2nd Punic War and ends with the Battle of Trebia. It is the first volume of a trilogy.
The main characters are three teenagers, Hanno (from Carthage) and Quintus and Aurelia (Roman citizens without the franchise from Capua).
The novel describes how the three become friends and how that friendship is tested in the face of war between their two cities.
There is a tension in such novels between creating characters that are believably of the time and yet are the kind of people that a modern reader can root for. I think Kane just about manages it.
He has populated his world with mainly unrealistically nice and honorable folks and some extremely nasty psychopaths with nothing in between.
He did give my ability to suspend disbelief a severe kick by choosing to describe the Carthage that existed at the time of the third Punic war rather the time of the novel. He really could have left that description out - as soon as I recognized one detail that was out of place I started doubting everything from then on. However, in the main the novel seems to be well researched with intelligent filling in of the gaps when the story drifts in to areas that we don't know about.
On one area I would have quite liked him to diverge from the sources. He assumes all reports of Carthaginian atrocities reported by Livy and Polybios to the absolute truth and merely attempts to give such events a pro Carthaginian spin to stop the Carthaginians appearing as monsters. At least some of those incidents must surely been Roman propaganda.
The plural in the subject is an invitation to others to add what they have read.