Sienkiewicz is my favorite historical-fiction author.
He wrote 'With Fire and Sword' 'Deluge' and 'Fire in the Steppe' (or Pan Wolodyjowski if you prefer)

Cornwell is a very intelligent and accomplished historical fiction writer.
Patrick O'Brian's style didn't click with me, but you can always try your local library.

Dumas writes some wicked ones to.