In a story I am about to write the best friend of the protagonist is a good, caring and benevolent person, lets call him John. The antagonist is not really a bad person but because of the circumstances in which he was raised is the villain, at least in the beginning of the story. Lets call him Bob.
Through some actions of Bob and especially his family, John starts to hate Bob and his mental states gets worse throughout the plot, while Bob starts to realize how wrong his actions are and his arc of redemption begins.
In the end, Bob is a redeemed villain and even becomes friends with the protagonist, while John has become kind of a fallen hero, who must be stopped by the protagonist with the help of Bob.
The problem is, that in order for the audience to really have a connection to both these characters (in addition to the protagonist) and care for the change in them I need to show their characters before the change. But as the protagonist also has quite some struggles (His best friend turns bad and he has to team up with the reason to stop him, the guilt of letting him fall, etc.) I feel like that is too much for one book. But on the other hand I see that as one story I don't want to be multiple parts.
So the question is: Is it too much for one book to introduce the new characters, the world, the magic system and in addition have so much character change, in which two people flip the sides with the explanation to why that is?