Also see the short and inexpensive paperback "The Knowledge Deficit" by
E. D. Hirsch.
What reading comprehension studies say is: To read with
comprehension (and to answer questions on a well-structured topic
intelligently), first you need to memorize extensive background on the
topic.
Science says that beyond the data in a problem, you can only reason with
elements of knowledge
that are well-organized in long-term memory.