I'm usually very careful with spoilers on this blog. If I do have to 'spoil' a book's ending to properly review it, for example, I always put up spoiler alerts; as I know many people prefer to avoid spoilers for books they haven't read. I can't say, however, that I've ever understood this. For two reasons; one, it seems to me that if you really want to avoid spoilers, you simply shouldn't read any reviews or comments on the book in question; and secondly, and following on from that point, I suppose I have a different idea of what a 'spoiler' is. Most complaints that I've seen voiced about spoilers concern the giving away of either the ending or major plot points. However, it seems to me that any review of a book is intrinsically full of spoilers for the potential reader, however vaguely it relates to the plot, because if it's a review worth its salt, it's going to give some kind of opinion about the worth of that novel, and, quite frequently, will comment on the characters and writing style. Although it might have avoided giving any information about the sacred plot, for readers like me, who are much more interested in how characters develop, reviews like this can be just as spoiler-filled. And, more broadly, knowing others' opinions of a novel before you begin it colours your view of it - whether you are predisposed to agree with them, or determined to dislike it because it's been so hyped, for example - and so these can be considered 'spoilers' as well.
With 'spoiler' redefined this broadly, it's obvious that no review can avoid spoiling a book. And I see this as a good thing. It's frustrating when reviews in the media dance around a topic, unable to give a full and considered opinion of a work because of the dreaded spoilers. Much better, I believe, to put up a generic spoiler warning and dive right in. Even if we take the word 'spoiler' in its narrowest sense - i.e. giving away the ending - there are many books and films that cannot be discussed properly without a consideration of the ending. I encountered this problem in my review of The Memory of Love, and was thrilled with the freedom I had in reviewing The Song of Achilles, where I was free to 'spoil' because everybody knows the story anyway (and surprisingly, they still enjoyed the book! Spoilers aren't that scary! Also see: The Other Boleyn Girl, Wolf Hall, etc, etc.)
So while I will continue putting up my spoiler alerts, I would prefer a reassessment of what really spoils a reading of a novel. Privileging plot information in this way, I think, not only short-changes those who don't care about it, but promotes a very narrow definition of why we enjoy reading books.