Your activation questions will depend on your purpose that's why no one can give you specific activation questions.
If you have to know the book consider turning the chapter heading and subheadings into questions. Create more than one question using the 6 w's Who, what when, Where , how and why.
Textbooks take longer than a 250 page non-fiction book. If you are taking that long for one chapter of a non-fiction book I suggest you check your purpose and shorten the activation time. Use a timer not just going in and doing it and letting it take as long as it takes. That's passive reading.
Alex
