December’s Book of the Month is Mathematician’s Delight by W. W. Sawyer, Dover Publications 2007 (originally Penguin Books, 1943).
This is Sawyer’s first book, and was written with the aim “to dispel the fear of mathematics.” According to the W. W. Sawyer website, it is probably the most successful math book ever written, going through numerous editions, translations into 10 languages, and selling more than 500,000 copies. It introduces mathematics with an emphasis on context: “Do things, make things, notice things, arrange things, and only then reason about things.”