I find it interesting that this non-fiction book on Germanic paganism bears in the English translation the rather romantic title "Gods of the Ancient Northmen" whereas the Danish translation has the more prosaic title "De Nordiske Guder" ("The Nordic Gods") and the French original text the more stiff and formal title "Les Dieux des Germains" - The Deities of the Germanic Peoples. I think that says a lot about how British, Danish and French audiences view the subject matter. Notice that the French are a Latinate, not Germanic people, and hence probably find Vikings and whatnot much more alien than say Danes or Englishmen do. However, this is a cultural gap which author Georges Dumézil does an impressive work to bridge over the course of this book's pages.
This is a short (about 150 pages) but densely packed book analysing what little we do know about the Germanic pagan religion practised by the viking era Scandinavians and the Iron Age Germanic peoples whom the Romans interacted with. Dumézil points out the many similarities to other Indo-European religions including Greco-Roman and Celtic paganism as well as Hinduism, which is where the really interesting information in here can be found. From there, he goes on to speculate what the religion of the Proto-Indo-Europeans looked like on the basis of those common elements.
I do think that in this part of the analysis, Georges Dumézil spins thicker layers of speculation than the available evidence supports. A good example is his theory that Tyr was the leader of the Aesir before Odin: Tyr's name in Proto-Germanic was Tiwaz, which obviously comes from the same PIE root as Greek Zeus and Latin Deus. (notice that the Roman name of Zeus is Jupiter, an abbrevation of "Deus Pater" that is "God the Father") Ergo, Dumézil reasons, Tiwaz/Tyr must have had a similar role in the Germanic pantheon as Zeus/Jupiter had in the Greek/Roman pantheon. The problem arises, if you look in the primary sources on the Norse mythology we have today namely the Poetic Edda: It turns out that Tyr appears in very few stories and in none of those does he play a similar role as Zeus. Jackson Crawford, an American expert in Old Norse and Germanic mythology, has a video on his YouTube channel where he explores what we know for certain about Tyr in deeper detail than I could.
Nonetheless, there is plenty of interesting information and analysis here. There is some sharp analysis of curses and prayers as they appear in the Icelandic sagas and the Poetic Edda, and what they say about the religious practices of the pre-Christian Germanic peoples. I also had no idea until reading Dumézil's book that not only does Hinduism have deities who are extremely similar to Odin and Thor - respectively Varuna and Indra - but also myths similar to that surrounding the blood of Kvasir as well as the end-time battle Ragnarok complete with gods that fulfil similar roles as Baldr, Loki and Hodr. I cannot remember their exact names, but Dumézil has gotten me even more interested in reading the Vedas, Upanishads etc than before.
People with an interest in comparative mythology and religion, as well as ancient cultures and how they might have influenced each other, would do well to pick this up if they have not already read it.