Audiobooks “typically ride on the coattails of the hardcovers. Because audiobooks are so fast, inexpensive and easy to record, the dynamic seems to be changing, with publishers looking to the audio format to fuel interest in paper books that aren’t quite ready for the printing press. And with the ubiquity of iPods, that interest can be generated quickly: recordings need not be pressed onto CDs and packaged, but can quickly be uploaded to iTunes.”