The mass-market edition of To Kill a Mockingbird will no longer be available in the U.S.

Just days after Harper Lee's will was sealed from public view, Hachette Book Group sent out an email to booksellers across the country announcing that Lee's estate would no longer allow mass-market editions of the classic To Kill a Mockingbird to be published.

The kill on the mass-market paperbacks, which are smaller in size and notably cheaper than trade paperbacks, will force readers to pay as much as nearly double the price for the classic novel, as Hachette's mass-market paperback sells for $8.99 while trade paperbacks sell for between $14.99 and $16.99. Due to the price difference, mass-market paperbacks are typically sold at significantly higher volumes than trade paperbacks. Since January 2016, 55,376 copies of HarperCollins' mass-market editions of To Kill a Mockingbird have sold, as compared to only 22,554 copies of the trade paperback editions.

The announcement is a particular blow to schools, which rely heavily on mass-market paperbacks. Lee's classic is currently taught in 74 percent of U.S. schools, but The New Republic notes that if schools aren't able to fork over the cash for the trade paperback editions, that percentage could soon decline.

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No explanation has been provided from Lee's estate. While mass-market paperbacks have generally been declining in popularity in the publishing world, To Kill a Mockingbird has been an exception. The New Republic reports that the estate will likely receive more money in royalties because of the switch.

Read the full story over at The New Republic.