Perhaps "The Little Red Book" isn't Mao Zedong's most influential work (and really isn't "his" book, but it is a collection of quotations from his other books and speeches and articles - though he is listed as the author), in terms of bringing about massive changes, like his previous books that led to the formation of the People's Republic of China, but it has sold a bazillion copies and is still read by people everywhere.
Books that changed the world (or at least some laws)
I was reading this post today, about a romance author who investigated the treatment of pregnant women in prison and ended up writing a bill (which passed with only one 'no' vote) banning the use of shackles for women in labor. The article is not for the easily squicked, it gets graphic in places, but the gist is that this author wrote a book that exposed some really hideous practices, added a happy ending where a law gets passed to prevent those things from happening, and then *made the happy ending happen in real life*.
That reminded me of The Jungle, by Upton Sinclair. While Sinclair was really interested in exposing working conditions and promoting socialism (oooh scary), his horrifying accounts of the meat industry in Chicago led to the eventual creation of the FDA.
I was wondering what comes to mind for others when they think about books that really made a difference. I'm sure there are tons of examples. So share! Or talk about the article, we can do that too :).
Perhaps "The Little Red Book" isn't Mao Zedong's most influential work (and really isn't "his" book, but it is a collection of quotations from his other books and speeches and articles - though he is listed as the author), in terms of bringing about massive changes, like his previous books that led to the formation of the People's Republic of China, but it has sold a bazillion copies and is still read by people everywhere.
I can't think of any books off the top of my head. Maybe because I mostly read senseless stuff, i will think on this!
But for a serious, non-fiction book - The Silent Spring by Rachel Carson contributed heavily to the launch of the EPA and the environmental movement as a whole by exposing the risks of DDT.
A book I have not yet read, but would like to - Ten Days in a Mad House by Nellie Bly. That's the one where the reporter pretends to be insane so she can get thrown into a mental hospital and then report on the conditions. The book resulted in major reform in caring for the mentally ill (and completely sane, for that matter).

Although even without the book we'd probably be at the same place
Thanks for posting it!