For a long time, books came int two flavors: hardcovers and mass market paperbacks. Then publishers added a third: trade paper. [Full disclosure: I'm old enough to remember when trade paper was novel. Excuse the pun.] Publishers can sometimes bring in quite a bit of money by publishing a book in all three formats. [That's what's happening with Face of Betrayal (Triple Threat Series #1), which has already been offered in hardcover and trade paper, is coming out in mass market paperback next month.
I think putting a book out as a trade paperback is a good option, especially in the cases they cite above. One thing the article doesn't do is distinguish between a paperback original that's a mass market paperback vs. a trade paper. I think there's a big difference, with mass market paperbacks being seen as a better fit for genre, not literary books. While the Oregonian, where I freelance review, does review trade paperbacks, I don't remember ever seeing it run a review of a mass market paperback.
The article also talks about how difficult it is to weigh the decision: "Frances Coady, the vice president and publisher of Picador, the paperback imprint of Macmillan, said: "You have to ask yourself questions like, 'Is it better to sell 5,000 or 8,000 copies in hardcover and try to reinvent the book in paperback?'—which, unless there's some extraordinary piece of luck, is really hard to do—or 'Is it better to sell 50,000 in a paperback original?'""
Read more about his sentence here.