I haven’t read as many Coolidge books as Derb, but I did enjoy the Sobel biography (which I reviewed here, along with a second book on Coolidge and a third one that dealt with him). Coolidge and the Historians by Tom Silver is also very good, though it isn’t the first Coolidge book anybody should read. After finishing it some years ago, I realized that I could never again trust anything written by Arthur Schlesinger, Jr., a relentlessly partisan historian and a great Coolidge hater.