I was struck by the similarities of these covers. The Fort was published in paperback in 2011 by HarperCollins; Imperium in 2006 By Arrow Books (a division of the Random House Group Limited, Great Britain).
Each book has the same ALL CAPS descriptor at the top, author name in red, same contrasty silhouette illustration style; although Cornwell's title appears gold (he sells more copies, so he gets the gold) both titles appear ALL CAPS, with a summary phrase at the bottom.
US book this year; UK book five years ago. Someone is stealing someone else's cover art. Or the same artist is stealing from herself. Or there is a formula for best selling historical fiction paperbacks and these two books follow that lead. Whatever the explanation, it's a bit disconcerting.
I'd love to hear from anyone who might explain this more believably...