I cannot speak to exactly what is in the PowerScore book...however I can tell you about critical reasoning on the GMAT. I have written over 100 GMAT critical reasoning questions that have been published and I also teach the LSAT, where critical reasoning is much more varied and difficult. I mention this because it is this experience that allows me to tell you the following:

On the GMAT there is usually just one conclusion in each stimulus (of course some stimuli have no conclusion) and only one truly important premise. The other premises tend to be more in the neighborhood of "background information." If you are working a GMAT CR problem from start to finish, taking notes I think you are approaching it incorrectly. Read the stimulus through once and identify the conclusion - then work it backwards, so to speak, deconstructing the stimulus and identifying the most important premise. The conclusion and the important premise - yes, in shorthand - should be all the notes you need for strengthen and weaken questions, (which together are much more than 1/2 of all the Official CR questions). Do not focus too heavily on everything that is written; much of what is written in each stimulus is not truly crucial. And remember to start and finish with the conclusion - it is the only thing that you can "strengthen" or "weaken."

In conclusion, if you are to take notes, I would simply note the conclusion and the crucial premise, rather than trying to take notes on each sentence. And remember - for strengthen and weaken questions you want to spend more time with the stimulus to have a general idea of the correct answer and look for that answer. At Veritas we have strategies for each of the various types of critical reasoning questions and however you choose to study for the test you should also develop methodologies for each type of CR question.

If you realize that the critical reasoning on the GMAT is often lots of smoke and mirrors trying to distract you - and if you refuse to be distracted - you may even find CR questions fun!

Good luck!