This is a thorough, very readable and excellently illustrated biography of Willem de Sitter (1872-1934), one of the most influential astronomers of his time, and also a co-author and correspondent of Einstein. Authored by a physicist and skilled writer, the book gives a beautiful and accessible description of the physics debated by Einstein and de Sitter, as well as the latter's alternative cosmological model, later known as the De Sitter Universe...