I'm never quite sure how accurate the history is, in the same way that I'm always a bit confused by Lucy and Andy Neanderthal. What's funny and what is something that actually happened? Oldfield apparently worked on some of the Horrible Histories, so I'll assume that the details are correct. Will the target audience care? The details are close enough to the truth that it's not going to make them make errors in their social studies papers or tests, and they just might have some fun information to share in class!
The British are far better at making history an appealing topic for readers, and Julius Zebra is a great addition to books like Stickman Odyssey, I Survived the Eruption of Pompeii, and Messner's Ranger in Time: Danger in Ancient Rome.