Helenora,
Learn the system on easy books first, so that you can apply them to the books you MUST read. If you can't do it in time to get the books you mentioned read, then just use regular reading. You're more accustomed to it. Unless you feel comfortable with photoreading.
Or, integrate some of the new techniques you've learned to help you comprehend the books you have to read at this point, before mastering photoreading. That is:
1)Photoread the books
2)Read them normally
3)Make mind maps
....etc. Not necessarily that, or in that order, but it's just an example to help you do better with what you need now, before you feel comfortable with photoreading enough to use the system without regular reading.
When I photoreading, I usually think of nothing. Sometimes I focus on my breathing, making sure it's deep and in a constant rhythm.
I always say the chant.
Sometimes I start to day dream while turning the pages. I don't mind so much, because I know that if I'm not processing the book consciously, I must be processing it unconsciously, and so I'm still photoreading.
Sometimes a few thoughts about the book pop into my head, but I don't really respond or hold on to them for long.
Typically, I focus on breathing and on the chant and I allow whatever happens, to happen.
Just stay relaxed, comfortable, and keep breathing and you'll be fine.