Sir Arthur Conan Doyle’s historical novels of this time period are worthwhile reading. Read The White Company first, then the prequel, Sir Nigel. While Agincourt isn’t involved, Sir Nigel involves Poitiers, another major battle of the 100 Years War. Both are available for download free at Gutenberg.org.
The Brigadier Gerard stories, set in the Napoleonic Wars, are a great read as well. (There is no relation between Sir Arthur Conan Doyle’s Brigadier Gerard and the historical French officer who became one of Napoleon’s Marshals.)