Amazon’s promise to complete the purchase of Audible as soon as possible following the completion of its tender offer last week turned out to be a couple of days. This morning, the growing e-tailer announced it had finalized its $300 million acquisition of the digital audio distribution, making Audible a wholly-owned Amazon subsidiary. Amazon’s $11.50 per share offer had been criticized by some shareholders, but in the end the overwhelming majority of stockholders accepted the deal.