Please tell us what you've been doing for manual activation? Have you drawn a mind map? how many activation sessions have you applied? How long is each session. Are you teating each chapter as a book in its own right or are you trying to activate the textbook as a whole.
Remember if there is a lot of information that you want out of a book (textbooks in particular) activate it in smaller sections or one chapter at a time. To avoid getting bogged down with the sense of overwhelm. Stick to time limits when activating the chapters and always make a mind map or record of some sort. Fail to make a record you fail to give yourself feed back of what you have found out. When you start building up the information you collect you can see how much you are, in fact, comprehending. Catch the small stuff first. It baits the bigger bits of information that naturally connect to it.
See my post on my experiment. Yes it's long so just scroll down to the "method of activation". It's what I did and how I did it to get information from a book where my regular reading method is shot. You'll also notice that my first activation session wasn't that crash hot. Had I given up at that point or even within the first 15 minutes of the session I would still have had nothing. It was only in the last 5 minutes that I found something that made a bit of sense to me. I put that on a mind map and I had a start. While I did it with a different language it is still the same hurdle when 'learning' something new. It wasn't until the end of the 3rd session that things it really started to come together for me. It's a bit like connect the dots it's not until you got most of them connected that you recognise the picture. http://www.learningstrategies.com/forum/ubb/Forum8/HTML/002346.html
BTW if anyone wants a copy of that to print for reference. You can copy and paste or email me for a copy. 
Alex
