ANN ARBOR, Mich. — Bookseller Borders, which helped pioneer superstores that put countless mom-and-pop bookshops out of business, has filed for bankruptcy protection, sunk by crushing debt and sluggishness in adapting to a rapidly changing industry.

The 40-year-old company plans to close about 200 of its 642 stores over the next few weeks. All of the stores closed will be superstores, Borders spokeswoman Mary Davis said.

The company also operates smaller Waldenbooks and Borders Express stores, including one in the Clearview Mall in Center Township.

Borders plans to operate normally and honor gift cards and its loyalty program as it reorganizes.

It owes tens of millions of dollars to publishers, including $41.1 million to Penguin Putnam, $36.9 million to Hachette Book Group, $33.8 million to Simon & Schuster and $33.5 million to Random House.

It has been a long fall for the Ann Arbor, Mich., company, which 15 years ago appeared to be the future of bookselling. But big-box bookstores have struggled as competition has become increasingly tough as books become available in more locations, from Costco to Walmart, online sales grow and electronic books gain in popularity.