“If everything is pointing to victory solving all real problems, throwing in such a hook at the end both blatantly shows the hand of the author and violates the structure of the novel.”
Example from a different medium: World of Warcraft - Wrath of the Lich King.
The Lich King was the Evil Puppetmaster of the Undead
that Blizzard had very successfully made you love to hate over the course of almost a decade before you finally got to kill him. As far as anything they ever said, he was in telepathic control of all undead, you kill him, it’s over.
Then, just before you’re about to kill him, a sage-type randomly proclaims that in fact, without him “The restless undead will be an EVEN GREATER threat!!” So somebody else has to take over and be the NEW Lich King! After all, we might want to kill him again in a later sequel…
“If everything is pointing to victory solving all real problems, throwing in such a hook at the end both blatantly shows the hand of the author and violates the structure of the novel.”
Example from a different medium: World of Warcraft - Wrath of the Lich King.
The Lich King was the Evil Puppetmaster of the Undead
that Blizzard had very successfully made you love to hate over the course of almost a decade before you finally got to kill him. As far as anything they ever said, he was in telepathic control of all undead, you kill him, it’s over.
Then, just before you’re about to kill him, a sage-type randomly proclaims that in fact, without him “The restless undead will be an EVEN GREATER threat!!” So somebody else has to take over and be the NEW Lich King! After all, we might want to kill him again in a later sequel…
Oh, yes. That's exactly the sort of thing that ruins series because you can't accept that series have to end.
A massive program to deal with restless undead would have made a cool new story.
Nothing more frustrating than the main characters who never end their story. After awhile, most readers get tired of the story and drop it.
Having a happy marriage that the main characters struggled to achieve in one book that quickly ends in the next book is almost as bad.
Not only is it a disappointment in itself, it means I can't believe in this book's happy ending, either.