To me, it still reads like “I was wrong” means “I was wrong about thinking that at least one of these was a better book”. Perhaps you could get rid of the sentence “I was wrong” entirely, and say something like “To my surprise, it turned out that for many people, this was not a believable conclusion.”
Oh. I meant there were many people to whom it was not believable. I’ll clarify that.
To me, it still reads like “I was wrong” means “I was wrong about thinking that at least one of these was a better book”. Perhaps you could get rid of the sentence “I was wrong” entirely, and say something like “To my surprise, it turned out that for many people, this was not a believable conclusion.”
I also thought you meant that Bill O’Reilly had (surprisingly) written the best book ever on the Lincoln shooting when you said “But I was wrong.”
Presumably “but I was wrong” was meant to be ironic. But there is no way to know that. Maybe say “But I was wrong according to O’Reilly fanboyz”.
The “but I was wrong” part is still unclear (consider what it appears to refer to).