yes it is non fiction
I would say FICTION.
non-fiction
Speculative Fictionor the more respectable branch of Science Fiction
no you need a non fiction book
Fiction
The genre that a non fiction book would be, would depend on its subject. Non fiction is narrative and factual and can be in many genres such as biographies, do it yourself, gardening, and art.
Which book "Eclipse"? Which author? There are more than one book called "Eclipse".
It is actually a fictional book it says a couple pages before the chapter that "this book is a work of fiction"
The story that I know called 'The Secret Garden' has only one scene in it that could be unreal in any level would be better called fantasy than science fiction. As a whole the story would not be a good candidate for the genre.
It is likely to be non fiction which is real because it is telling you facts .
Orson Scott Card has a wonderful book called How To Write Science Fiction and Fantasy. Ben Bova has a book called The Craft of Writing Science Fiction That Sells. These books may be at your public library or you can buy them on Amazon. They would be very valuable to explain how to write science fiction. You may also want to attend writer's panels at science fiction conventions and meet other authors, publishers and editors.
Most would refer to it as a historical novel. It certainly would fit the genre of novel. It might also be called something like an Elizabethan or Victorian novel, depending on the specific time frames.