How do you guys feel about unreliable narrators??

Personally, I have mixed emotions about them. In some cases, the author can make it work. For example: Gone Girl by Jillian Flynn. The diary entries were a great way to pull it off. She meant for the diary to be found, which is why she was pretending to be something she wasn’t. If it’s something like that, it tends to work well. Letters to another person, or if something happened to make the narrator unreliable. A mental illness or a head injury for instance. What I don’t like, however, is when they are unreliable for absolutely no reason at all. Like, when the ending comes, and it’s completely unbelievable because the narrator has been one person throughout the entire book all the way up until the end and then they have a complete personality switch out of nowhere. It doesn’t make sense to me. One book that does this is You Shouldn’t Have Come Here by Geneva Rose. It’s written in the style of Gone Girl. The book switches back-and-forth between the perspectives of two different narrators, male/female. We are put into the minds of both individuals throughout the book, then at the end, the unexpected twist comes, and suddenly they are no longer who we thought they were at all. But there’s no reason for the random personality shift whatsoever. it comes totally out of nowhere and is just extremely unbelievable/unrealistic. It’s almost as if the author were in a hurry to finish the book, and just completely changed her characters into totally different people and scribble down some random ending for the sake of finishing the book. There’s no foreshadowing or any type of clues leading up to the twist at all. I don’t like this. It left me with a lot of confusion and unanswered questions. How do you guys feel about unreliable narrators? In your opinion, when do they work and when do they not? Feel free to provide examples for both. Books where the author makes it work, and books where they don’t.

Note: I only ask to provide examples so that I can see what your idea of a good unreliable narrator is versus a bad one. That is not a recommendation/suggestion request. Examples are not necessary. I would just like to know how y’all feel about unreliable narrators in general. I hope this post doesn’t get removed because of the last sentence!!

Edit: after another person mentioned it in the comments below, I would like to add that another type of unreliable narrator I happen to enjoy is one that has a distorted view of reality for some reason. For instance: they are extremely immature or self-centered, they are paranoid, they are being gaslighted by someone important to them, etc. One major example I can think of is My Dark Vanessa by Kate Elizabeth Russell. The teenage protagonist, Vanessa, is being gaslighted by her teacher who is 27 years older than her. She is so traumatized and blinded by his gaslighting that she thinks they are in love. She doesn’t realize that he is a predator who has groomed her to fall in love with him. she is so unreliable, in fact, that we as the reader actually believe it’s love as well until we start to see the truth about midway through the book. Sadly, though, Vanessa doesn’t realize it until the end.