January’s Book of the Month is Famous Problems in Mathematics by Heinrich Tietze, first published in German in 1959, and republished in 1990 by DTV. An English translation published by Graylock Press in 1964. The preface contains a beautiful metaphor and explanation of the nature of mathematical learning.
The original work is entitled Gelöste und ungelöste mathematische Probleme aus alter und neuer Zeit.
The full English translation has the title Famous Problems of Mathematics: Solved and Unsolved Mathematical Problems from Antiquity to Modern Times.