I skimmed the book, a fifth edition from 1974. Totally comprehensive, combining biology and genetics with the cultural and social, it's pretty impressive. Some political and historical context also backs up arguments and forms the basis of chapters, which is always good too.
Personally, I simply read for more information on the subject of 'race', but Montagu's arguments were convincing in refuting the very idea of racial difference itself. Particularly enlightening chapters: 4. the biological facts, 6. "Race" and Society, 12. "Race" and Culture. The Jewish and African American chapters were particularly candid in dealing with sensitive subjects, and the Appendices worth reading too.
Giving it five stars because I don't believe other reading on race would be necessary for the casual reader: it's all here. The book is well organised and the writing is top quality (though with some outdated terminology in the edition I was reading).