Sideshadowing allows the reader to stop looking at the narrative and its timeline linearly and instead consider the set of alternate possibilities, viewing time as “open” just as in real life.
To my mind, for a number of years, the gothic genre meant horror. Eerie looking witches. Haunted castles. High-pitched screams. Dark. Damp. Depressing. But that’s not all that the genre is.
Great storytelling is more just a great story idea. If it’s not written well, the reader is unlikely to be entertained enough to want to read through till the end of your novel. This where a literary device like foreshadowing can lend massive depth to your plot, to the characters and to the dramatic effect, something you cannot afford to leave out if you want your readers to be hooked to your book.