Potential for a twist: The book is part of the forest's soul, and destroying it would destroy the forest. The protagonist has to find a balance. Or the book can only be accessed when the forest's temperature (literally or metaphorically) is right, hence "Cio" (heat).
Make sure the story has a beginning, middle, and end. Start with the premise, build up the mystery, develop the conflict, and resolve it with a meaningful conclusion. Maybe the protagonist learns that some knowledge is meant to remain hidden, or that balance must be maintained. Livro No Cio Syang Baixar
Also, consider names for characters. Maybe the guardian is an ancient entity with a name in an old language. The protagonist's name should be simple, maybe something like Elia. The forest is Syang Baixar, so the guardian could have a name that's a play on that or something mystical. Potential for a twist: The book is part
Need to add elements that tie the fever aspect into the book's effects. Maybe the book's power is tied to the seasons, causing a literal or metaphorical heat. The title is in Portuguese, so maybe setting the story in a Portuguese-speaking country, but that's not necessary. Focus on creating an atmospheric, mystical setting. Make sure the story has a beginning, middle, and end
Need to make sure the story flows logically, characters have depth, and the conflict is compelling. Maybe include a myth or legend about the book among local townspeople. The climax could involve a ritual to destroy the book or a sacrifice to stop its curse.