1) pg 258, Figure 12.8a. In the line drawings, the slopes are written as dy/dx and a/b. The dy/dx is correct, but the other one should be b/a, not a/b (assuming it's written as y/x, but otherwise the dy/dx should be dx/dy).
2) pg 270. Keyboard.readString is actually Keyboard.readLine in the API.
3) pg 277, 2nd to last line: expect should be except.