I came across this website, which is run by parents who wanted to know more about the content/appropriateness of the books their kids were reading.  It has reviews of books, which include language, themes, etc.
I thought it might be helpful to some others.  I haven't perused every section, but it's a great idea for those of us who just can't keep up with what our kids read.  We have long since passed the time when I could actually read books ahead of my kids and weed out the ones that I though were not appropriate for their age/stage.
Here's the link . . .
http://bookalachi.com/