it is a mature and serious story, it touches on serious and heavy themes, especially in the MC's past, I recommend that you read this review before starting to read
in a world where villains, heroes, and mutants exist, and it is not DC or Marvel, being apparently an original world of the author, the MC who has the power to control "threads of destiny" ends up in an accident with a portal in the middle of a conflict between all these forces and find himself in the world of the witcher
the story already begins with the MC unconscious in the witcher, being watched by Keira and Triss, the beginning of the story is not one of the most ... sympathetic ... because the MC is manipulative and efficient to the extreme, as written in the synopsis from the author "past evil MC", he will do anything to achieve his goals, and I mean anything, the power of his destiny is like a link that allows him to see the past of the connected people, control them (barely use, bcz he is wanting to change), in addition to seeing the future in a few minutes, plus a few other things that I won't spoil.
the MC is a machine of brutal efficiency because his disturbing past made him that way, and everyone he controlled and used in the past with his powers was as bad as him or worse, don't be mad when MC act like they were puppets, bcz they did the same or worse to others. But after he travels to the world of the witcher he sees it as an opportunity to start over, realizing that his personality is not adequate as he has no morals or ethics, he decides to change, taking the short-term goal to become more " human", and long-term... well it hasn't been said out loud yet, but he's learning magic and shows an interest in Genetics, as well as wanting to open up a transport business, but that last one is pretty questionable as it's been said in passing and Triss thinks that it might just be a passing thought for him not to go crazy, creating a goal to keep him going, because he knows he would go crazy without one.
the story tackles heavy themes like R@p3, genocide, and infanticide, all driven by revenge. however in a superficial way to explain MC's personality, without delving into many details, mainly with the omniscient narrator talking a little about the MC's previous world and his past
the other characters also have depth and are very similar if not identical to their original counterparts, I can imagine Triss and Keira acting precisely the way they did, they have their feelings and fears, even fearing the MC's powers and his indifference to ethics and morals.
In conclusion, it's a dark, serious adult story that tells of a broken man starting over and going down a path of redemption, together with the ones who believe in him, with a heavy focus on slow but noticeable character development and interactions, relationships, feelings, sympathy, love, and fear.