Looking for a book which portrays a character's confusion very well/clearly or has them feel more disconnected from the world throughout the story

I'm looking for inspiration for a story I'm trying to think up, I want to know the most effective way to portray the main character's immense disorientation and confusion at the beginning without it coming across as poorly written.

Any book which is a good read which has a point in the story where the main character is very confused or disorientated and the writer portrays it very clearly/well.

And any book where the main character slowly changes throughout the story where they start to lose their humanity or sense of right from wrong where they feel so disconnected from the world that it seems meaningless to care due to gaining some kind of power or new perspective, kinda like Dr. Manhattan from Watchmen.