what genre and style did it follow?
Fiction
The Coral Island
 is greatly occupied with the realism of domestic fiction 
what is the coral island? It is a novel. who is the author of this novel? It is written by a Scottish author. what is the historical context behind it? It began a trend in boys' fiction by using boys as the main characters.
wiki:10704706
The Coral Island [SEP] Genre and style
Romance, with its attention to character development, was only restored to the genre of boys' fiction with Robert Louis Stevenson's "Treasure Island" argues literary critic Lisa Honaker. "The Coral Island", for all its adventure, is greatly occupied with the realism of domestic fiction (the domain of the realist novel); Ballantyne devotes about a third of the book to descriptions of the boys' living arrangements. The book exhibits a "light-hearted confidence" in its description of an adventure that was above all fun. As Ralph says in his preface: "If there is any boy or man who loves to be melancholy and morose, and who cannot enter with kindly sympathy into the regions of fun, let me seriously advise him to shut my book and put it away.