How can I ask a teacher to follow the textbook more closely?
You may certainly ask -- politely! -- but you should expect to be told "no", and you should accept that answer if it is given.  In most graduate courses, it is the privilege of the instructor to decide what are the important points and how to organize them.

If the course is preparation for a qualifying exam (for instance), then there may be a more rigid syllabus that needs to be adhered to.  In such a case, if the instructor were deviating strongly from the expected objectives it would make sense to complain.

As an aside: since the book presents things so well (from your perspective), you can learn the material from it and consider the lectures as supplementary.  It then seems to me that having lectures that approach things from a different perspective than that of the text is a benefit.  An instructor who parrots the text would be redundant.