From Wikipedia:
Well-known bestseller lists in the U.S. are published by Publishers Weekly, USA Today, The New York Times and The Washington Post. Most of these lists track book sales from national and independent bookstores, as well as sales from major internet retailers such as Amazon.com and Barnes & Noble
If the book I author appears in Publishers weekly, NYT, Washington Post or USA today as a bestselling book, before the close date, then this market resolves yes.
If all of these lists cease to exist, then resolves N/A. if any of them still operate, then they count.
Related questions
@ItsMe you're using the wrong group when calculating base rates. Consider base rates of someone who's been top writer on fanfic or Wattpad like sites
@MichaelWheatley If the co-authoring is a significant enough thing to make it so that both authors share the authorship, then it counts. Assistance to another for writing their book doesn't. Something like Good Omens counts:
@firstuserhere Thanks. I was afraid of another AI Letter situation so I'm trying ot work out all the angles.
@firstuserhere the longest thing I've ever written was 8 years ago, a 15k word long story centred around death and regret.
(Excluding any theses written)
@Stralor YES! I have wanted to for many years and have written short stories and even attempted Nanowrimo challenges! Speaking of that, maybe I could do it this year as well, would be a fun exercise