Recently Krugman has been defending textbook economics, arguing that if policy makers had simply followed their advice, the crisis would have been far less severe.
It is deeply unfair to blame textbook economics either for the crisis or for the poor response to the crisis. (Krugman, The Trouble with Economics is Economists)
I don’t dispute that austerity has made the crisis far worse, and that conventional IS-LM analysis argues for government stimulus, not austerity, in a severe recession. But the extrapolation that therefore mainstream economics textbooks are fonts of wisdom is nonsense. They are instead enormous exercises in often unintentional mendacity–omitting huge swathes of economic research or empirical data when that research or data contradict mainstream beliefs.