Books related to popular anime?

[lelouch]

I've started actually reading books more often lately, and I was wondering if you guys had any suggestions for books that have similar storylines to popular anime. I'm looking for something that has a similar plot to things like Code Geass, Gundam Seed, Legend of Legendary Heroes, etc. Basically something where it starts out with two people who were close at a young age, and then due to whatever circumstances were separated and joined opposing factions and were later forced to confront one another on the battlefield. Multiple suggestions would be very much welcome and appreciated.


EDIT: Movie/series suggestions would be appreciated as well!