I do limit (censor) DS's book selections. First, for practicality in regards to number. Secondly, in terms of age appropriate content and scariness.
Though I see no need to make restrictions on too easy books in our families current situation, I can imagine reasons why other families might feel a need. For instance: They may have been there specifically to get a book for a school book report. The parent may feel that the teacher would reject the too easy book, necessitating another trip to the library.
About the research showing that kids who read drivel for pleasure grow up to be adults who read drivel for pleasure... Does it do anything to show causation as opposed to simple correlation? Also, is there any research that shows that reading large amounts of drivel as an adult is of any value beyond the momentary enjoyment of the drive?. I read a lot of drivel, and an occasional useful book/magazines/news here and there. My eldest sister reads tons of drivel, and almost never anything particularly useful. My middle sister read a little drivel and occasional useful books/etc. My Dh reads practically no drivel, and a little useful books/etc. Guess which ones of us have the higher paying jobs?
What the research tells us:
1. Children who are allowed free choice in their pleasure reading are more likely to still be reading for pleasure as teenagers.
2. Teenagers who regularly read for pleasure score higher on measures of verbal ability and vocabulary.
3. "Lifelong readers," which we define as individuals who read often, and eagerly, for multiple purposes, throughout their lifespans, frequently report that a great deal of their reading is not particularly intellectually edifying-- series books, for example, or romances.
4. Adults who are lifelong readers raise children who are lifelong readers, and lifelong readers don't confine themselves to edifying classics-- they read a wide variety of whatever catches their interest, for both learning ("useful books") and for enjoyment ("drivel.")
We also know that reading is about more than getting a good job or going to a good college, and that "reading to learn" is only one kind of reading. Reading for relaxation is the key ingredient in the lifelong habit of reading. It is a habit that can bring a lifetime of joy and pleasure and learning into a person's life. We know that being overly controlling with children's reading choices often leads to them abandoning the habit of joyful pleasure reading. And we know that any reading at all contributes to one's skill as a reader-- the ability to read more easily and quickly, which is called fluency-- and that skillful readers tend to read MORE, which in turn builds further skill which further contributes to the enjoyment of reading. This hand-in-hand relationship of enjoyment and fluency seems to be what creates a lifelong reader.