For me endings are the most important section of a book. It's my final impression, the thing that sticks in my mind and usually does a great job of wrapping up a story with characters I love. But sometimes it doesn't quite work that way. Most of these endings aren't "bad" endings, some of them are just too tragic for me to recover and one of them was so confusing that it's three years later and I still don't understand. There will be spoilers ahead so be wary (I've tried to avoid specifics but it was hard)!
The High Lord by Trudi Canavan
The original book that broke my heart. This is one of my favourite fantasy trilogies of all time. And it's definitely not a bad ending. It's a great ending. But oh god my poor baby heart. My absolute favourite character dies right after everything starts to go better for them and I just. Every so often I start thinking about what could have been if they had survived. This is one of those character-deaths that I just took way too personally. But again - not a bad ending - a great one and if you haven't read this series already I highly recommend it!
Tempest by Julie Cross
This book is the reason I don't often read time travel. Some backstory for you in case you haven't read this - the main characters girlfriend dies. So he goes back in time (more or less by accident actually) to fix it. This all happens right at the beginning by the way and is in the blurb I believe so not a spoiler. Now the spoiler-y part. He changes the past so that he and his girlfriend never met, which meant she was never in danger because of her association with him and so never got shot. But my problem comes when - if she didn't get shot - he had no reason to go back in time. Which means none of the time travel stuff happened, which means nothing got changed. I just can't handle the paradoxes here so never continued the series.
Allegiant by Veronica Roth
What would a list of Endings be without this book? Honestly I wasn't even that saddened by this character death. I was just mad. For a variety of reasons it felt unnecessary and whilst I can handle tragic endings I do get annoyed when the tragedy seems thrown in for dramatic effect or to be a talking point. Which I guess worked since I'm talking about it now. But still, this ending soured a series that I otherwise really loved.
Gone Without a Trace by Mary Torjussen
This is the "mind blown" entry on the list. Another great ending. I just did not see it coming at all. For this, and a number of other reasons this has become one of my benchmark thrillers and all other books get measured against it.
A Tale of Two Cities by Charles Dickens
Because obviously. This is honestly the best book ending ever. But my heart. The first time I read A Tale of Two Cities I threw my copy to the other side of my bed in anger and said "No" so loudly my Dad came in to check I was OK. I instantly regretted it because I have a gorgeous copy of A Tale of Two Cities but it remains in my mind as the only book to ever make me so angry/sad that I had to actually throw it.
Alice's Adventure in Wonderland by Lewis Carroll
Just the worst. I love this book. It was the first book I ever read and it's framed so much of my love for reading. But dear god that ending. "It was all a dream". Really? REALLY? No. Just no.
Let me know what some of the endings you'll never get over are - either the great ones that stick in your mind, or the bad ones that made you mad or ruined a book for you!