Although there are plenty of historical details, this is the least historical-feeling of all of The Roman Mysteries books I've read so far. Instead, with its friendly, sort of mystical dolphins, evil octopus, shipwreck and treasure, it feels a bit like a typical middle grade adventure novel. That doesn't mean it's not a good story. In fact, I loved the descriptions and felt like I was transported to Pliny's villa and the beautiful sea around it - a very nice "vacation" of sorts.
I did feel the "mystery" in this one was a bit underdeveloped, and some part of me also felt like Lupus' backstory didn't quite go with what we've learned about him in the previous books so far, not to mention his general reaction to Vinalicius. But then, it's been a while since I read the previous book in the series, not to mention since I started this series overall, so it's possible that I just didn't recall the right details.
The way things wrapped up also in some ways felt too easy or neat, but not entirely unrealistic or hard to comprehend.
Whatever the case, as with the other books in this series, the characters are engaging, we learn a bit about everyday life in the Roman Empire. And in this case, we get transported to a magnificent seaside villa and get to swim with friendly dolphins - hard to complain about that!
One overall note: I'm reading these books as an adult with some knowledge of Roman history. But for young readers who maybe haven't studied Ancient Rome much, it's a shame that there aren't illustrations, at least from time to time.