My opinion is Power score is already an old bok . Well the concepts are still valid and the approach too. However, I do not think that it stigmatize how to approach CR now, in this moment on real gmat.
Looking at it with the eye of the beholder, MGMAT CR
5th edition OR Aristotle CR are the best book.
Moreover, on line (and on this board) for free there are a plenty of sources to achive the best result in terms of proficiency.
KUDOS is the good manner to help the entire community.