I hate it when a fantasy story basically abandons the original plot or tone because the author realizes it makes sense based on the systems they set up in the novel.

I don't get why this is so common in fantasy novels. The author sets up a fantastic world that feels live in and real, and by the end of book 2, they abandon the pre-established plotlines that existed in earlier novels because things set up in book 2 could lead to that hypothetically happening.

I'm looking at you Stormlight Archive.

Spoilers for later books in Storm light archive: The story starts out as a world with strict social groups where the different characters hold different roles within that group. Kaladin is the low class peasant who tried to rise above his station and was betrayed and made into a slave. Shallan is someone from the upper class whose family is destitute and she's forced to move in unsavory ways to ensure her family isn't knifed because of the shady deals her father made. Dalinar is at the peak of the upper class. He's trying to find a way to win the war his people are stuck in. Tonally, it's very dark, very serious, and the magic system feels grounded and reasonable.

Yet by book 4 we're talking more about how different powers intersect to allow more powerful flying super people and growth of technology rather than spending any time figuring anything about the past out. Not, going into books 6 and beyond, it looks like we're going straight sci-fi. Space travel, interplanetary conflicts. Mixing different magic systems from within the cosmere together and getting even more over the top convoluted magic bullshit.

Book 1-3 were great because we weren't stuck so far within the magic system's ass that we can have real conversations about religion, belief, and class disparity. But by book 4 Sanderson is more interested in how you can make planes with the magic powers than caring about the slow social developments that would result from rapid changes in society.

Every nobel who would push against the change in society was basically killed in book 3, so now the racial conversation is dead because no one cares about old money vs new money dynamics.

But this isn't a post on r/brandonsanderson it's pushing against the faults in a process of writing.

So who else does it?

Honestly, the book that does it FAR worse than even Storm Light is a small title called Super Sales and Super Heroes, where a character can modify items he owns, so he buys a superhero by mistake and can change their stats. Pretty normal LitRPG, except, in book 2 we go from having the author have him learn how to best utilize his power and the morality of his power, and go interdimensional hopping where he all but abandons earth for some Isekia bullshit only to end the book by having the author himself talk to his character and say "ya, no more of that."

I feel like everyone knows sort of what I'm talking about. You start a book about a low class assassin who falls in love with the person they're meant to kill and has moral qualms with their mission, only for book 3 to be all about how the assassin was always royalty and is explaining basic kindergartener morality to nobelmen because the assassin grew up in a farming village or some bullshit.

That isn't to say this can't be done well. I honestly think He Who Fights With Monsters handles the transition rather well, because books 1 and 2 establish mechanics, but even when the main character is talking philosophy, he's still harping on the same ideas he cared about in book 1. The author is still allowing the character to look back on ideas he had in book 1 and he allows the character to see how they just don't work.

But what's the difference between He Who Fights With Monsters and Storm Light Archive?

Simple:

HWFwM doesn't abandon it's original tone and ideas while Storm Light does.

Storm Light starts as a gritty story with a dark society, and ends with book 5 having everyone acting as each other's therapists and pushing healthy mental health.

HWFwM starts with a character who thinks he knows everything and isn't willing to move against his morals even when everything would be easier if he just did. It always looks to be tonally dark and always hits on expanded but similar beats.

It's natural for a book series to expand and progress. For Wheel of Time to go from kids traveling to the big city, and end with characters playing politics and blowing up entire cities with anti-existence beams. For Mistborn to start with bringining down an authoritative tyrant, and end with killing god. Those are both fine, because the progression feels natural and the tone doesn't shift. But so many stories start with "We're here to do something unforgivable in a fantasy setting." and end with "We need to get into the star ship to escape planet X from being blown up in our goal to bring down the evil interplanetary tyrants."

You hooked your audience with the fantasy tittle, why did you decide to write a totally different book half way through?