Beazley, C. Raymond. Prince Henry the Navigator, the Hero of Portugal.
and of Modern Discovery, 1394-1460 A.D. London: G.P. Putnam's Sons, 1895.
This biography from the "Heroes of Nations" series puts the achievements of Prince Henry the Navigator in the context of the development of the maps of the known world and Portuguese history with a particular emphasis on navigation and explortation in the C14th.
Symington, Martin, et al. DK Eyewitness Travel Guide: Portugal. London: Dorling-Kindersley, 2016.
This is a comprehensive and well-illustrated guide book packed with well-indexed information. Great for research and entertaining reading.