Readers tend to choose what they already know when reaching for the next book. That's what BookBub, one of the leading advertising hubs for books, said in a report from a recent newsletter. The ad site's studies of book buyers showed that readers most often got their next book because they liked the author. At No. 2, and a close second, was buying the next book in a series.

The results about book choices included some surprises. Way down on the list, just 17 percent of buyers said they picked their next book because of the cover. Right underneath author and series familiarity? Plot. At the bottom of the reasons books were purchased was critical reviews.

Some of these results fly in the face of accepted wisdom. "Produce a great cover" is among that advice, along with "Go all out to get great reviews." There's a caveat here, in that the readers are looking for another book and will give an author who they already know the first shot — so long as they like the plot, or the previous book in the series.

The takeaway advice for an author starting their career is to have plans for more than one book. If not a series, at least multiple titles. You could always carve up that 500-page opus into two books, tying them together with a great plot. Have the same artist do both covers. If you can afford it for awhile, offer the first book for free.

This is the kind of advice a publisher should give you, should you choose to take the traditional route and give away 90 percent of your cover price in exchange for writing, rewriting after an edit, and marketing. Yes, you'll do that last one in the list. You're always the CEO of your books, and nobody wakes up every single day thinking about selling your book except you. Authors, start your platforms, and think about multiple books.