Sorry if this is not the right place to ask but I'm looking to find whatever is considered the most authoritative biography or nonfiction work on Richard I.
There are a lot of popular history books about Richard, but the best academic ones are probably John Gillingham, Richard I (Yale University Press, 1999), and Jean Flori, Richard the Lionheart: Knight and King (trans. Jean Birrell, Edinburgh University Press, 1999).