I think the 4th edition of Manhattan's RC does have a number of good drills that well help you improve your RC skills. Beyond reading for scale, the book also focuses on using context clues to determine words you are unfamiliar with and it has a chapter on section salvaging when you only have a few minutes for a passage. It is certainly no silver bullet but I do think the book is good.

The real silver bullet of RC is doing a lot of passages. Pull out the RC section from the 30 earliest PT's and do them section by section until it starts to click. The structure of passages are similar and it is this repetition that really allows us to make major gains in reading comprehension.