F-train commuters were in for a pleasant surprise this morning, thanks to a "guerilla art" group called the House of Malcontents. The all-female quartet boarded the third car of a train at Coney Island in the wee hours and turned the weathered space into a living room — laying down welcome mats and rugs, hanging flowers from the poles and curtains over the windows, replacing MTA safety posters with paintings and family photos, and turning overhead billboards into mock bookshelves. (Authors represented ranged from Albert Camus to Zora Neale Hurston.) Officially, it was a commentary on how much time Gothamites spend on the subway, but leader Ellen Moynihan admits there was another goal. "We wanted people to talk about something at work besides what they watched on TV," she said. Critics included one unamused cop and a woman irate about the cost to advertisers, but by midtown, people started whipping out camera phones. "It's adorable," legal secretary Beatrice Beccari said. "It'd be nice to have more [of this] instead of ads for dentists and cosmetic surgery." Naturally, most riders pretended they saw nothing. —Michael Y. Park