Definitely 'The Sword in the Stone' by T.H. White. It sets the stage for the Arthurian tales with a lot of medieval - style elements including knightly training and small - scale battles. 'The Black Arrow' by Robert Louis Stevenson also has a medieval setting with warring factions. And 'The Book of the New Sun' by Gene Wolfe has elements of a dark, medieval - like world with battles and quests.
Sure. 'The Knight' by Gene Wolfe is a great read. It's about a knight's journey and the battles he faces. Another is 'Gates of Fire' by Steven Pressfield, which gives a detailed account of the Battle of Thermopylae in a way that has a medieval - like feel of honor and combat. And 'A Distant Mirror' by Barbara W. Tuchman, while more of a historical account, reads like a fictional story of the 14th - century warfare and society.
I would recommend 'The Iron King' by Maurice Druon. It's part of a series that delves into the power struggles and wars in medieval France. 'The King Beyond the Gate' by David Gemmell is also good. It features a hero who has to fight in a war - torn medieval - like world. And then there's 'The Warlord Chronicles' by Bernard Cornwell, which focuses on the Arthurian legend from a more gritty, war - filled perspective.