Just read this history book, by a UCLA English professor whom I don't know personally, and liked it very much.
The book is about the last judicial trial by combat authorized by the French central government, in 1386; it seems quite thoroughly researched, but it's also a page-turner. It's got friendship gone sour; a battle to the death; a complaining witness (the wife of one of the combatants, who had accused the other of rape) who would face immediate burning at the stake (on the grounds that she had been proved a perjurer) if her husband and champion was defeated; and a battle scene that's shocking even to me, after all the battle scenes I've read about and watched in movies.
This would make a great historical movie, it seems to me; but in any case, it should be a great gift for your history buff friends. Here it is in (And, no, I'm not getting a penny from this plug.) Here it is in paperback and in hardcover.