Artistic License History / Trojan Odyssey

• Max claims Egypt was given this name by the Greeks from a location mentioned in the The Iliad, which gets it backwards. The word "Aígyptos" was not an exonym, but just the Greek spelling of "Hikuptah" ("The Home of Ptah's ka"), an earlier native name for the Egyptian capital of Memphis, so its naming has nothing to do with a random literary source. Furthermore, while the first usage of the Greek word remains unknown, there is no reason to believe it was coined by the author of the Iliad, as contacts between Greeks and Egyptians predate the esteemed dating of the text.
• She also claims Egypt first received this name when Alexander the Great invaded it (presumably on the location from the Iliad mentioned above), which is, again, wrong pop knowledge. Herodotus already referred to Egypt by that name half a century before Alexander was born, and as mentioned, he was not the first to do so.
• In general, the book describes ancient Celts as if they were a single, defined civilization, with all of their tribes from Spain to Denmark sporting the same recognizable weapons, customs, culture, religion and technology - something that is effectively a historical aberration. Even if archaeology and history had not proved the exact opposite of this notion (to put only one example, Celtiberians and Gauls were at least as different from each other as Greeks and Romans were, and geographically speaking, they were only separated by the Pyrenees), this would be soundly unlikely due to the enormous differences in geography, possibilities of development, and exchanges with neighbor cultures they would have sported.
• The in-universe historians, supported by the images in the ancient tomb, also claim ancient Celts fought naked most of the time, which is just a popular belief that a bunch of supposed experts should know better than. The Gauls were the only Celtic tribe that sported something similar to this custom, and whenever they did it, it usually amounted to fighting merely bare-chested. Full, unambiguous nudity was only recorded with certainty among two very specific Gaul groups, the Gaesatae and the Tolistobogii.
• Similarly to the previous, it is claimed that Celtic women fought all the time along with the males, with the tomb showing nude Amazons as a proof. This is another stereotype that cannot apply to all Celtic tribes: the only real instances of Celtic women coming out as regular fighters happened in the last days of the Lusitanian Wars and maybe during the Roman conquest of Britannia, and it was under very special (and desperate) circumstances each, not as an usual custom by any stretch of the expression. (Ironically, you would open a can of worms if you simply called Lusitanians "celts" in front of an Iberian antropologist, as the matter is not so simple; the mainstream view, by no means the only, is that they Lusitanians were rather a pre-Celtic people who got Celtized at some point.)
• Only Gaul and Britannia had "druids" by that name, as ancient chronicles only mention them in those countries, while at the same time give hints that other Celtic lands like Hispania had rather different religious classes (the Hispanic counterpart to a druid was apparently a kind of diviner called "hieroscope" in Greek). Also, even although we know little about them, it seems there were also great differences among the druidic orders of the two former countries. This at least might be justified because it is Epona, a Neo-Pagan cult leader and therefore not a reliable narrator, the one making the claim.
• Warriors sporting bushy moustaches instead of full beards is given as a pictoric proof of them being Celts and not Greeks. In reality, this distinction doesn't exist, as beards were common in Celtic cultures too. Only Gaul noblemen sported those characteristic moustaches with the chin shaven.
• Ancient Celts had a very primitive political system, based mostly in regional chieftains who ruled small tribes, occasionally conjoined in larger monarchies, so the possibility of a gigantic alliance of Celtic countries from all Europe in 1200 BC would have been downright impossible. Even larger-than-life figures like Viriathus and Vercingetorix failed to unify the lands equating to modern Spain and France, not to talk about creating a multi-national alliance (and those two had the advantage of being influenced by more advanced cultures like Greece, Carthage and Rome, so they were not even earlier Celts like the ones from the novel).
• The experts from the book also seem to support the witch-cult hypothesis, a disproven conspiracy theory about how European witch-hunts were actually a mass attempt to suppress undeground pagan holdovers. Even more bizarrely, their explanation about the topic also seem to mix the conquests of Rome and the expansion of Christianity as if it was a single event.
• It is claimed that Greek gods might have been actually early Celtic gods that received different names. This is true in the sense that most European pantheons descend from the ancient Indo-European gods, but to say that the ancient Greek religion was an appropriation of its early Celtic homologue is a very bold (and very wrong) claim.