The legions of reporters and commentators following every move by Robert S. Mueller III, the special counsel, do not know when he will finish investigating Russian interference in the 2016 election. And it is unclear whether the report he is expected to file will ever become public.

That hasn’t stopped two publishers from setting a date, March 26, for when people can buy their book versions of the eagerly anticipated document. One online outlet is already describing one of those books as a bona fide hit.

Amazon’s listing for “The Mueller Report: The Final Report of the Special Counsel into Donald Trump, Russia and Collusion,” carries a “best seller” label based on pre-orders. On Barnes & Noble’s website, the publisher Skyhorse is promoting the $9.40 paperback — with Mr. Mueller and the Department of Justice as authors — as “required reading.”

For $10.50, readers can also put in an advanced order for “The Mueller Report” from The Washington Post and the Simon & Schuster imprint Scribner, which bills the report as “the most anticipated investigative document of this century.”