These maps are beautiful - I think the Hobbit one, with Smaug curled around it, is my favorite.
Not sure exactly how to rank this vis-a-vis "books," though. (I actually haven't read the little supplement book that comes with the maps - perhaps I shall!)
John Howe is an artist that worked on the LOTR trilogy and drew the four beautiful full-colour poster maps that make up this collection: maps of northwestern Middle Earth, Wilderland, Beleriand and Numenor. The maps are accompanied by some brief notes by him about the process, as well some essays from Brian Sibley (fairly lightweight) about the importance of maps to Tolkien's creative process and the difficulties and challenges he had in drawing them (eventually taken over by son Christopher), as well a gazetteer of all the places named on the maps. The book was a birthday present from my son and makes a gorgeous gift to a Tolkien fan.