So you hate spoon-feeding pablum to the kids and really wish you had some books to quietly get them into thinking mode, eh? Good for you. Not every child needs to read fluff. Not every child *wants* to read fluff. And oh, what conversations you might have after reading some of these great books.
Let's start with our old friend Dr. Seuss. Old Ted was a G-E-N-I-U-S in my view. Horton Hears A Who! is all about tyranny of the majority and making sure that even the potentially unpopular minority voice is heard in the world -- "a person's a person, no matter how small!" The Lorax (Classic Seuss) is a cautionary environmental tale of how greed will one day destroy our natural resources. The Sneetches and Other Stories educates about how crass commercialism will part you from your hard-earned money, and for what?? So you can think you are better than someone else? All because you have a star on your belly? One classic which I think is often overlooked (and how easy it is to overlook a Seuss book -- there are so many, and they are all so wonderful!) is Did I Ever Tell You How Lucky You Are? (Classic Seuss). Children need to know that there is always someone else out there who has a worse lot in life. Definitely check out Dr. Geisel and his many works -- I can't say I loathe any.
Another author who is terrific when it comes to subversive literature is Roald Dahl. People are most familiar with Charlie and the Chocolate Factory, but let me introduce you to Matilda. It's a great place for kids in the 6-8ish department to start realizing that grownups are not infallible. Most of the grownups in the book are truly grotesque caricatures of anti-intellectualism at its worst. Soon after reading this, my 6 year old daughter connected the book with The Wall, which is probably not wildly appropriate for little kids in full. But she knows the words "we don't need no education, we don't need no thought control." And the headmistress and parents in Matilda are the reasons that songs like "Another Brick in the Wall" were written. Those adults were never interested in true learning.