i read scanned pages that you posted. Book is correct. you are getting problem in making a switch for stretch and when you keep the condition to 1 joints get overlap or disappear . i think you have done a mistake in renaming the things, make sure you have correctly renamed the Ik handle, effector and other things as mentioned in book. sometime it happens when we try to fix things in hurry and we do small small mistakes. ok. So just repeat your process once more or check if everything is renamed properly and all nodes connected in right manner. good luck!