My favorite book by Paul Krugman is Peddling Prosperity,
which I once assigned in a course and still often recommend to students. A reader recently reminded me what the book says about the use of fiscal stimulus (page 32):
When monetary expansion is ineffective, fiscal expansion...must take its place. Such a fiscal expansion can break the vicious circle of low spending and low incomes, "priming the pump" and getting the economy moving again. But remember this is no by any means an all-purpose policy recommendation; it is essentially a strategy of desperation, a dangerous drug to be prescribed only when the usual over-the-counter remedy of monetary policy has failed.Update: Jon Henke says that Paul has consistently expressed this view.