One popular 'isekai ojisan light novel' could be 'Isekai Ojisan: Isekai ni Tensei Shita Kedo Cheat Nanka Shinai yo'. It tells an interesting story about an uncle who gets isekai -ed but doesn't have the typical cheat skills.
For me, 'That Time I Got Reincarnated as a Slime' stands out. The world-building and plot development are really engaging. Also, the characters have a lot of depth.
Well, it's a bit hard to pinpoint exactly which was the very first one. But some early examples could include 'El-Hazard: The Magnificent World', which had elements of the isekai genre.
Isekai Quartet indeed has a manga. It offers a different perspective and sometimes delves deeper into the story compared to the anime. The manga can be a great companion to the animated version for fans wanting more of the Isekai Quartet world.
I'd recommend checking out online manga libraries such as Comixology or Crunchyroll Manga. They often have a good selection of isekai titles. Also, some local libraries might have physical or digital copies you can access.
I'm not entirely sure as I haven't read it in detail. But generally, it might be about some sort of fantasy story involving a bishoujo (a cute girl character in Japanese media) and an ojisan (uncle or older man) in a novel - like setting.
Isekai manga is a genre where the main character gets transported to another world. It's different from others because of the focus on this world-jumping aspect and the adventures that follow.
I'm not sure who the main characters are exactly as I don't know this work well. But from the title, it seems that a bishoujo and an ojisan would be important characters.
For must-read isekai manga, 'Sword Art Online' is a great choice. It combines action, adventure, and a touch of romance. The virtual world it creates is both exciting and immersive.