Amazing story, character development, world-building, fantasy elements, impeccable foreshadowing, exciting progression, rationality, consistent quality... This story has everything.
Set in a typical magical European world with wizards, trolls and other familiar creatures you, it involves the concept of the MC repeating a time loop which always repeats from the same checkpoint. The main character is a wizard who aims to make use of the time loop to get strong, learn about and stop a huge invasion on a city by the end of the time loop. He keeps growing in abilities and personality by practice and learning from his mistakes. The name of the novel is derived from a latin proverb "repetition is the mother of learning" after all.
This concept of time loop allows the author to repeat similar scenarios with very interesting changes after every reset depending upon the changes in actions of the MC in the time loop. The novels takes 'cause and affect' very seriously and its a very interesting aspect of the novel. The MC learns from his mistakes and uncovers various mysteries related to the major events of the loop. The author of MoL takes maximum advantage of this feature of stories involving time loops and after every loop you learn about many interesting details about the world and secrets and mysteries about the events in the loop along with the MC.
What makes the mysteries or details so interesting in MoL is that its fantasy elements are very detailed, consistent and sensible and its always interesting to learn more about it plus it has some interesting lore. The fantasy elements is one of the best things about this novel and is precisely why i think its one of the best in the genre. If you've seen hunter x hunter or naruto you must've been interested in learning about their magic systems more. The magic system of MoL is way more detailed, logical and interesting than them. I've never seen a fantasy that takes the fantasy elements so seriously. If you are like me who expects detailed explanation about the fantasy elements of a series, them this novel is just for you. It has many branches of magic like mind magic, combat magic etc. and all of it is very detailed. The MC starts almost from zero magical skills but keeps growing with various fields of magic through practice. The practice doesn't involve mindlessly throwing laser from a wand but is actually pretty logical and satisfying to learn about.
The MC grows not only in abilities but also in personality. He learns from his mistakes in social situations and keeps maturing. He is pretty mature even before the time loop starts for a 15 year old. So its satisfying to see him develop. His logical reasoning is pretty solid and its satisfying to see him take realistic logical decisions. Apart from him all characters have a realistic and consistent behavior.
On top of all this the world of this novel is pretty big and has lots of interesting lore. This makes learning about it all the more fun. If you enjoy logical and detailed series which are also fun, then this is for you.
Other than all this, it is pretty easy to read. The author doesn't give a lot of descriptions about the looks of people and places which I feel isn't very important because the reader can always come up with it on their own.