A few thoughts, with my professional hat on:
I too am a little worried by the idea that we need, as parents, to be pushing our children into reading more difficult and/or challenging books, and that reading has to be "work." There is absolutely nothing wrong with a child reading books that come easily and effortlessly-- this is a good, positive thing. It builds fluency. It contributes to the enjoyment of reading. It is what lifelong readers do. We read things that challenge us-- of course we do, sometimes, when there's something we want to learn, or a book that is important enough that we're willing to do the work. But we also spend many, many happy hours reading trashy romances and sci fi novels and fashion magazines and horror series and all of the other kinds of "mind candy" that are in print.
In fact, the research on lifelong readers, and on what practices best encourage a lifelong love of reading, are overwhelmingly in favor of allowing children to choose what they read, and in favor of the "junky" series books that so many parents and teachers are down on.
http://edina.k12.mn.us/concord/classrooms/media/parents/seriesbooks.pdf
for example was a very important study of these issues that many people will find comforting, if their child is seemingly "wasting" time reading books that seem mind-numbingly easy or trite. These books are the stuff on which a lifelong reader is built, in fact.
Quote:
Feitelson and Goldstein (1986) found that light reading provides motivation for more reading. Students who read books in series (several books written about the same characters) developed reading fluency and the linguistic competence necessary to read higher quality material. They gained knowledge of the world, learned story structures, and became aware of literary devices by reading series books. Light reading became a stepping stone to further reading. Increased reading proficiency and fluency makes it possible for students to read more complex material. They often choose light reading for independent reading because they enjoy it, and they become more fluent readers in the process. Adults who encourage students to develop the reading habit through light reading can lead them to further reading. Students must take the first step of developing reading fluency before they can take the second step of becoming avid readers.
http://www.ala.org/ala/mgrps/divs/aasl/aaslpubsandjournals/slmrb/slmrcontents/volume32000/independent.cfm
I've never seen any research at all that requiring children to only choose challenging books is of benefit. I have seen loads of research suggesting that freely chosen voluntary choice is a huge factor in whether students read for pleasure, and whether they continue reading for pleasure once they reach the age where parents can no longer require that they do so. And I've seen plenty of research to support the idea that children and teens who read for pleasure consistently score higher on measures of achievement in verbal ability and vocabulary. And I've seen plenty of evidence that repeated reading of "easy" texts is highly supportive to the growth of fluency and enjoyment. And I've been working in this field since 1998, as a reading specialist.
so while I encourage him to keep stretching himself I wont make him return a book that is deemed too easy/hard
 i read anything and everything i can get my hands on, drives dh nuts. 
