I am enjoying your book immensely. But I have one small nit to pick. Every now and again, you pose questions in the body of the book ( not the exercises) which may not be answered by the text of the book itself. For example. Page 211. A question to ascertain why class methods cannot access instance variables. A quick glance at the index, does not readily answer this. This is very frustrating. I would suggest, humbly, that you keep these questions for your exercises, or put aside some space at the end of each chapter to answer these. Now I **think** I know why, but this is a very fundamental aspect of understanding how different methods work, so it's nice to know if one is correct.