Mine is "The Children of Húrin by Tolkien" (writer of The Lord of The Rings books).
Q:What makes it depressing?
A: Good guy gets captured by Bad guy. Bad guy imprisons Good guy on side of mountain. Bad guy curses Good guys children. Throughout the book, the Good guys son ends up killing his own best friend on accident, leading an army to destruction, marrying his sister without knowing it and impregnating his sister. Sister finds out truth and kills herself. Brother finds out truth and kills himself. Father gets released from imprisonment by bad guy. Father finds his wife by side of road. Wife dies in his arms that night. Book ends.
Q:What makes it depressing?
A: Good guy gets captured by Bad guy. Bad guy imprisons Good guy on side of mountain. Bad guy curses Good guys children. Throughout the book, the Good guys son ends up killing his own best friend on accident, leading an army to destruction, marrying his sister without knowing it and impregnating his sister. Sister finds out truth and kills herself. Brother finds out truth and kills himself. Father gets released from imprisonment by bad guy. Father finds his wife by side of road. Wife dies in his arms that night. Book ends.