Books with an egotistical, but genius main character

If anyone’s seen code geass, I’m looking for a book with someone similar to lelouch or Light from Death note (incredibly smart but also egotistical). Some themes of the above anime: Drama, war, psychological etc.

The main character doesn’t necessarily have to be egotistical, as long as they are far smarter than everyone else.

Would prefer if these books are old(er) and generally involve psychological battles (similar to references above).

Thanks!

by 47q_