This isekai-fantasy (takes a lot of regular young people to this other "world") is dark, violent and emotional. If I were to compare it to a popular war movie, it would be like "Platoon", "Hamburger Hill" or "Apocalypse Now". This other "world" steamrolls the process of bringing/taking people from Earth and getting them here. Regular girls and boys, with no special martial arts skills, no real abilities that are supposed to start from bellow zero to adventure, survive or die. The people brought here die all of the time, with no resets, no redo's, no second chances.
The Dark, violent and emotional, contrast with the lack of emotional intelligence by some of the main characters. Some people believe that it's a kind of "realism", but "realism" in fantasy-fiction is like having sails on a car, or putting plastic/wood chips on food, and working only on the Holidays... The thing is, Fantasy/Sci-Fi Fiction needs to be rational, logical and make common sense.
The powers that be bring lots and lots of young people to this world, but do nothing to train them, clothe them, feed or shelter them (except the 10 silver for signing up). There are no tutorials, no basic/boot camp training, no one that can help or lend a hand. The main characters are the extreme "left-overs" (people that lack charisma, lack physical prowess, lack intelligence and nobody wants in their "physical education" team...)
I first started reading this light novel series after seeing the first season of the anime, the anime does not have the extreme violence, the extreme fear, the possibility of starvation/living out in the streets if the "volunteer soldiers" do not succeed in this really tough, dangerous and dark place... The anime does not have the constant bullying and sexual harassment that the character Ranta constantly has with everybody in this group of misfits/left-overs...The other people in this "team" are too shy, too incapable, too introverted, to have been sent to this other "world". People really die here, the reference to "ash" in the tittle is to all of the people that have "tried, failed and died" in this other "world". They have all turned to ash...All of the bullying and sexual harassment made me stop reading this series (about 5-6 years ago) at around volume -7-8-9 if I remember correctly...
Things could have been better in this other "world"...The people isekai-ed could have received "basic training", basic food and shelter while they are becoming efficient at combating the monsters found in this place...But this is why this Light novel series in particular is an "atypical" isekai light novel series...That seeks to show how regular people would suffer and die if they do not rise to the challenge of "overcoming the monsters" and becoming economically independent in this other "world"... The "game-like-system" in this other "world" lacks balance. Does not train well the people that come, does not choose the professions that are best for them, along a long series of other problems...
The author believes that sacrificing the best people to protect the weakest, whiniest, incapable is a fair exchange. While all of the worst main characters were constantly complaining, the "Christ figure" in this first book assumed all of the responsibility all of the consequences and for what?? So that the readers can be tortured time and time again by the bully and sexual harasser Ranta, and the rest of the sub-par, whiny, weak and stupid main characters???
There is no warning for all the violence, the blood and gore, the extreme fear or futility that the author constantly transmits throughout his story...The illustrator has his own drawing style and makes everybody a little bit too hairy and elf-like (reminded me of the characters in The Dark Crystal... So, if you have never felt depressed, felt despair, had real reasons to worry about the future, never really experienced a school of hard knocks, then a story that is "raw" like this one, might be something interesting for you to read...