Disclaimer: You’ll have to take my review with a grain of proverbial salt as I dropped the series after reading volume 7 due to a broken heart. However, I will one day pick it back up due to how great this series is...
Firstly, this is a vastly underrated series. This may be a worthless claim, seeing as how commonly tossed around it is, so without further ado, here's why:
The strategies the author writes for the battles that happen are clearly above and beyond. The characters do not win because of incompetent enemies or with simple, dumb strategies. The author clearly has done their research into
military tactics of the past and comes up with plausible strategies that are truly well-developed. In addition to the great strategic writing that makes the series realistic, we get a depiction of war in its complete lack of glorification. It showcases the brutality of war. People die. You will lose people you love- no one is exempt from death in battle. It's not happy. There is no glory and honor in war.
The author does not try to maintain a plot where the characters are protected from major suffering. There is not an overly optimistic plot that is all too common in anime and LN's.
The fine balance of fictional elements with realistic elements also separates this story from most other anime/LN stories. It starts slowly with a higher ratio of light-hearted fictional tropes (i.e. Ikta being a playful womanizer) to the harsh brutality of war to introduce you to the characters. As the story progresses, as you become attached to the characters and their growth, the story's ratio of light-hearted elements (such as playful banter) begins to drop as the scale of conflict grows.
The characters are forced into unwanted situations. They make mistakes, their judgments are not perfect, and they will experience loss and consequences to their actions.
I highly endorse giving this series a chance. But as I said in my disclaimer, the plot progressions may not move in the optimistic direction you hope for. It may break your heart. But such strong emotions are a sign of the strong, creative writing of the author.
If you thought the strategy in Code Geass or Arslan Senki was interesting, the level of tactics and strategy used in this series is a complete realm above those two, blowing them out of the water as the story progresses.