In general, forenowledge of any kind expressed in a book is a significant challenge. A prophecy introduced in the beginning of a fantasy novel can either make the rest of the plot boring, or force the oracles to be smugly obscure. This type of thing seems to be more prevalent in fantasy books. Even handled as a flashback mechanism, foreknowledge is not easy to handle well. It is important to note that the best books sometimes transcend the most fundamental rules.
Extroardinary skill can overcome many sins.
Sometimes even deeply flawed books from beginning authors are interesting, because of originality, or some other aspect. However, in most cases, these do tend to be exceptions .