The authors are uniting. Last spring, when Amazon began discouraging customers from buying books published by Hachette, the writers grumbled that they were pawns in the retailer’s contract negotiations over e-book prices. During the summer, they banded together and publicly protested Amazon’s actions. Now, hundreds of other writers, including some of the world’s most distinguished, are joining the coalition. Few if any are published by Hachette. And they have goals far broader than freeing up the Hachette titles. They want the Justice Department to investigate Amazon for illegal monopoly tactics. They also want to highlight the issue being debated endlessly and furiously on writers’ blogs: What are the rights and responsibilities of a company that sells half the books in America and controls the dominant e-book platform?