Adrian Tchaikovsky 
One Day All This Will Be Yours [EPUB ebook] 

Welcome to the end of time. It’s a perfect day.Nobody remembers how the Causality War started. Really, there’s no-one to remember, and nothing for them to remember if there were; that’s sort of the point. We were time warriors, and we broke time.I was the one who ended it. Ended the fighting, tidied up the damage as much as I could.Then I came here, to the end of it all, and gave myself a mission: to never let it happen again.