Only two English kings have died on the battlefield. Richard III at Bosworth Field in 1485. And Harold Godwinsson at Hastings in 1066.
This is a very detailed account of Harold's life and the life of William the Conqueror (he used to be known as William the Bastard until he started winning stuff). But for all the detail, and politics, it's still a really good read.
And he included my favourite part of the battle of Stamford Bridge.