It's a story that likely involves complex and perhaps dark themes. However, without reading it in detail, it's hard to say precisely. It might be about some sort of macabre or extreme situations, characters dealing with death in unique ways, and complex relationships within a rather unusual setting.
It's a light novel that typically involves elements of mystery, action and the supernatural. It follows a unique storyline with its own set of characters and their intertwined fates.
I'm not sure as I haven't read the novel. But typically in such a story with a title like this, there might be a character who is somehow connected to death, perhaps a reaper - like figure or someone who has a special ability to deal with death - related matters.
The main characters in the 'dead mount death play light novel' are not widely known to me at the moment. However, typically in a light novel like this, you would expect to find a central character who has some special qualities or abilities. There may also be characters that are either friends or foes to the main character, each with their own backstories and motives that contribute to the overall plot of the novel.
Some libraries also have collections of manga. You could visit your local library and see if they have Death Note. Another option is to look for digital libraries or apps that offer manga rentals or subscriptions.
Choso is not dead in the manga. The plot hasn't taken that turn. Usually, character deaths are significant events and for Choso, that hasn't happened yet.