Reinhold Niebuhr, The Children of Light and the Children of  Darkness: A Vindication of Democracy and a  Critique of its Traditional Defense, hardcover,, 1944, Charles Scribner's Sons, very good clean condition.  This book has a pencil inscription that the previous seller claimed was  Niebuhr's. I doubt that it is in Niebuhr's hand. The former owner was Ronald Larson who likely new Niebuhr so the claim is possible but the initials R N. do not appear to me to be his.  Nevertheless, it is a classic book by a mid-20th century Christian thinker who was widely influential including on Martine Luther King, Jr., and more recently a president of the United States.  If you can prove that the "R.N." is in Neibuhr's hand you will have a treasure, otherwise you have an important work at a very reasonable price.