Amazon is already facing a potential lawsuit from the Federal Trade Commission, and now, a group of authors, booksellers, and an antitrust think tank is calling on the agency to investigate the e-commerce giant’s stranglehold on the bookselling market, as previously reported by The New York Times.

In the letter, the Authors Guild, American Booksellers Association, and Open Markets Institute urge the FTC to look into Amazon’s “monopoly in its role as a seller of books to the public.” The three organizations accuse Amazon of dominating “almost every aspect of the book market,” citing data that the company sells over 50 percent of all physical books in the retail market, 90 percent of physical books sold online, and over 80 percent of all ebooks on the market.

As alleged in the letter, Amazon’s dominance in the publishing industry, plus its full control over the bookselling process, means “nothing is stopping it from using its control to harm publishers, booksellers, readers, and authors as it continues to line its own pockets.” Amazon, which first started out as a website for selling books, has grown to become a major player in the publishing industry, creating its own Kindle e-reader and operating a self-publishing platform. The company also owns the book review site Goodreads along with the bookselling website AbeBooks.

“Amazon has an oversized power to control what readers see when browsing for books. Only Amazon understands how its algorithm works,” the letter reads. “Amazon can up-rank and down-rank titles at a whim. As Amazon steers readers towards its own titles and away from rivals, many readers end up buying books that are less relevant, less interesting, or of lower quality than had they been able to choose in an open and competitive market.”

In recent months, numerous reports have emerged that the FTC is readying an antitrust lawsuit against Amazon, and it could happen as soon as this month. Amazon is expected to have a “last rites” meeting with the FTC this week, which typically takes place before a lawsuit is filed, according to Politico. It’s still not clear whether the FTC will target Amazon’s dominance in the bookselling industry, but some of the arguments outlined in this letter are hard to ignore.