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Though it is spattered with stage blood from beginning to end and features the sort of carnage associated with Eli Roth movies, “American Psycho”turns out to be one of those musicals that send your thoughts awandering, even as you watch them. So while this show’s title character (played byBenjamin Walker in an admirably disciplined performance) takes a gleaming ax or chain saw to his co-stars, you may find yourself fixating on the following questions:

Collectively, how many hours of gym time per week does the incredibly buff cast embody? More than that of the acrobats of Cirque du Soleil, whose“Paramour” opens on Broadway next month? Did those auditioning for “American Psycho” have to submit ab shots instead of head shots? And before they set foot onstage each night, are they required to pass a body mass index test?

If such queries do indeed fill your head during the long and decoratively gory duration of “American Psycho,” which opened on Thursday night at the Gerald Schoenfeld Theater, then it could be argued that the show’s creators have done their job. This is even more true if envy gnaws at your bowels at the sight of all those hardbodies (to use one of the script’s favorite words) prancing and posing before you.

That means you’re thinking like Patrick Bateman, the surface-obsessed, unceasingly covetous, all-depersonalizing antihero of this production, adapted by Roberto Aguirre-Sacasa (book) and Duncan Sheik (songs) fromBret Easton Ellis’s notorious 1991 novel, and directed by Rupert Goold. Of course, it could be argued that the “American Psycho” team has done its job too well, since you’re also likely to identify with Patrick when, shortly before he crucifies a young woman with a nail gun, he concludes solemnly that there’s “not one clear, identifiable emotion within me.”

Though it often looks as carefully and cosmetically arranged as a window at Barneys, Patrick’s favorite store, and features a gray-toned, red-splashed, World of Interiors-worthy set by the in-demand Es Devlin, “American Psycho” is a mess. That’s not because of all that sloppy, sloshy blood, but because of its terminally undecided tone. And it’s not the kind of mess you wallow in, hooting at the glorious chaos of it all. Its conflicts of intention cancel one another out, leaving you numb.