Fanatsy, male main charcter, fiction, Don't know the age but it is at least a few years old not new.
I remember a good deal about the early parts of the novel, thankfully, in the beginning, the main character is in prison for murdering a gang or an evil organisation. It was pretty brutal, according to what people said, he killed the gang because they killed his wife? Someone very important to him, at least, then he and a lot of other people got summoned to an area (tower/dungeon) level and forced to try and live after they managed that, they could leave the tower/dungeon and found out they are in a new world and that the people in that world summoned them to clear the tower/dungeon and the meathed they used makes it so they have a countdown for how long they can live if they don't enter the tower/dungeon.
This is about all of the details of the plot I can remember, but there are a few more things to help.
The main character refuses skills from the tower/dungeon because it changes a person's memory to teach them that skill, and he refuses to let anything change his memory.
The main character, I think, was called Josh, not too sure on that though.
The tower was the main focus, but the main character did do other stuff
Oh, and I read the book online, I don't think the book even has a real-world vision, although I could be worng