Rethink Books, the provider of a digital book distribution app called bookshout!, has closed on $6 million in Series B financing. bookshout! allows readers to interact and share reading-related thoughts and notes on social platforms like Facebook and Twitter. The recent financing came from Ambassador Enterprises, a VC firm based in Fort Wayne, IN. Rethink Books also raised $2 million in its Series A round of financing, as well as $750,000 in seed.