Washington bookstore Politics & Prose -- which two years ago refused to host a reading for cybergossip Matt Drudge because, in the words of co-owner Carla Cohen, "he's a rumormonger and a troublemaker" -- is once again ruffling conservative feathers. This time, American Enterprise Institute scholar Joshua Muravchik says the independent bookstore agreed to sponsor a signing for "Heaven on Earth: The Rise and Fall of Socialism." But then, the author complains, the store's events coordinator withdrew the invitation when he belatedly realized that the book is critical, not laudatory, of the leftist ideology.[...]