One really appreciates the “pocket” label of this format if one wears suits, sport coats, or blazer jackets, or almost any of several styles of coat that fall under the category of “overcoat”: these books really were pocket size! For those pockets, that is. The thicker ones are pushing it, but the ones closer to 250 pages fit neatly in a blazer pocket. Thicker ones are fine in the cavernous pockets of many overcoats (though, hell, so are trade-size books)

(Phones work better in a jacket, too—I think we made a mistake running away from that clothing style, they’re like wearable purses that also make you look nicer. Sure suits are kinda wasteful with the way the jackets get downgraded if the pants are destroyed, but odd jackets we should have held on to!)

What's confusing to me is that even most of the the print-on-demand services I've seen for self-published writers don't go below trade paperback trim sizes (5x8 inches).

There's a huge amount of indie fiction that really wants to be in pocket-size mass-market print format (for those buyers who prefer paper to ereaders), for ergonomics and some of the pulp aesthetic, but it's forced to trade paperback trim.

The format is going strong in Japan.