This book is creepy as hell, for several different reasons. My skin crawled on several occasions. At times I had to think about putting it down and walking away for a while. Given that the edition I was reading was only 88 pages, that's saying something!
Lots of spoilers ahead - in fact, most of the review. And potential trigger warnings.
And what is mostly the freakiest is what is implied, not said. The potential for ghosts is all on the top, as is the potential for madness. What is strongly implied but not ever quite said is the most upsetting. And anyone who doesn't want to read about or discuss sexual abuse of children should probably take a break from this one.
Because that's definitely the implication that's hanging in the air. And the main character's reaction is possibly the most upsetting thing to me. Once she comes to these conclusions (rightly or wrongly - it's certainly what the housekeeper thought was going on, but the children don't really ever quite do anything that backs it up - the letter from Miles' school might be indicative and it might not), she vacillates between seeing the children as poor victims and seeing them as newly evil creatures that she cannot save.
It is this that I find the most disturbing, as it's what the book dwells on in the most detail. On finding two children who might have been abused, her reaction is to regard them with revulsion and suspicion. At times, anyway. The view that this now means that they're unutterably corrupted, beyond redemption, in any way at fault, well, that turned my stomach. We don't know that that's the way everyone would regard them, but it's certainly the tack the governess takes. The housekeeper is not nearly so extreme.
And this horrific possibility definitely unhinges the governess, whether to madness or sheer horror, it's hard to tell. What, after all, is the evidence? She carefully avoids ever broaching the subject to either child, to asking them about it, to doing anything that would in any way involve the children or gauge what they are actually thinking or doing. It's this dehumanization that haunts me far more than the ghosts.
So yes, this is an incredibly creepy story, even all these years later. It makes my skin crawl just remembering it. I don't think I'll be revisiting the story, but it certainly was effective.