For a light novel, The Saga of Tanya the Evil focuses less on “light” and more on “novel”. Unlike most other light novels, these books are not quick reads. This series reads at the same pace as a regular novel with an equivalent page count. Readers who have watched the anime will notice the books start a little differently. The anime begins with a flashforward before going back and explaining previous events. The book, on the other hand, presents the information chronologically (for the most part). While reading this first volume, keep in mind the book’s title Deus Io Vult is the Catholic motto “God wills it” that was popular during the Crusades.
The structure of Deus Io Vult is a bit difficult to follow. New readers may have trouble picking up on Tanya’s circumstances in this strange new world. Tanya’s story starts in our world as a middle-aged Japanese salaryman. The circumstances of his death lead to reincarnation on an alternate Earth. As a baby girl. In a country that is essentially pre-WWI Germany. And (s)he grows up just in time to join the military just as the war starts kicking off. Gender pronouns are actually tricky with Tanya, as (s)he is physically female but still thinks of him/herself as a man.
Anyway, every good isekai (trapped in another world) series has something different that makes it stand out. In this case, it is the story being in the military genre. Most other isekai series take place in standard fantasy worlds with knights, wizards, and so forth. While magic does exist in this world, they are still on the level of WWI technology. Magic is just used to amplify that technology. For example, a magic-charged rifle bullet could have increased explosive force, allowing it to function as a mortar shell. The series presents a very unique mix of magic and not-quite-modern technology.
The writing style here is a bit clunky. There is a lot of detail in the world-building and story, making the book long-winded for a light novel. Tanya also frequently makes real-world references, with cliff notes at the bottoms of pages for readers unfamiliar with those topics. Overall, this is one of the better light novel series out there, especially for readers interested in military history. It is different from most other light novel series, so people looking for a quick read might be turned off. If you are on the fence for this one, I highly recommend checking out the anime first.