One piece of advice 20 minutes is an excellent lenght for an activation pass.
First activation pass 30 minutes for the whole book this means regardless of lenght "the whole book". For a textbook this means you only have time to become familiar with the structure some of the sections you will identify what they are about others you won't. For regular books you may have time to discover everything you need to know. Your 10 to 15 minute postview will have triggered areas of interest and you will have dipped a little more into them.
Next activation passes you go directly to areas of interest. Remember to dip when you get the urge to do so however superread and skitter. You're looking for answers for the mind probing question you formed.
Do you expect to be finished with a book after 30 minutes? You expect to be finished when you're finished and met your purpose, If your purpose is only to spend 30 minutes with the book to see what you can know about the book in that time then thats means you're done in 30 minutes. You going to know everything about the book? Not consciously. You decide what you need to know and how much more you want to know. Keep going with additional 20 to 30 minute activation passes.
Reason I personally recommend 20 minute; so that you stay with superreading and dipping. If you allow yourself to spend more than 30 minutes with the book without reconsidering what you want out of it you falling into the PASSIVE reading trap.
I am afraid if you follow Photoread4me's advise you are actually just 'regular reading' with perhaps a bit of a sense of purpose thrown in. However it becomes passive as soon as you give it too much time.
Alex
