Peter Biskind probes the mental currents of the '50s through its films

There's a catchy dust jacket on Peter Biskind's new book, ''Seeing Is Believing: How Hollywood Taught Us to Stop Worrying and Love the Fifties,'' published by Pantheon.

The background is a stylized movie screen. On it, a teen-age werewolf menaces a bobby-soxer. He's all decked out with a varsity jacket and pearly fangs. She looks a bit old for a high-schooler, but true to the book's subtitle, she sure looks worried - and yes, maybe it's about the '50s, the only decade in which a monster quite this wacky could have stalked the screen.

Biskind's thesis is that movies reflect their society in countless and subtle ways that become more apparent as time goes by. Details of story, character, and behavior that once seemed - well, normal - can be wildly revealing a few years later.

The '50s aren't exactly ancient history yet, but enough decades have passed to make a backward look worthwhile. Take that teen werewolf, for example. At the time, the quickie horror flick he starred in seemed like just another avatar of youthful rebellion, which was a big issue of the Eisenhower age. Biskind takes another look and finds a symbolic struggle going on - ''conservative demonology against pluralist ideology, sorcery against therapy, Transylvania against Vienna.'' This may be overblown, but hindsight has its benefits. In 1957, after all, who could have known this hairy monster was the first hippie?

As words like ''conservative'' and ''pluralist'' hint, ''Seeing Is Believing'' takes on politics as well as film. Concerned with ''what we see when ideology becomes visible,'' Biskind spends many pages pigeonholing movies, dubbing this one ''corporate-liberal,'' that one ''right-wing radical,'' and so on.

Although this gets tiring after a while, some of the insights are valuable. In the courthouse drama ''12 Angry Men,'' for instance, Henry Fonda doesn't just prove his fellow jurors are wrong when they condemn an innocent defendant. Rather, he actively wins them over to his side. Since consensus was a key value of the '50s, this is therefore a ''centrist'' movie, and since the hero feels ''compassion for the victim,'' it's a ''corporate-liberal'' movie, too. Meanwhile, the conservative characters slide toward the center as the film proceeds, much as Republicans gradually accepted the New Deal.

Biskind is at his best finding nuances of story, behavior, and technique that reveal unspoken Hollywood biases. ''The Thing,'' a conservative film, signals that a man is sneaky by giving him a Russian-style hat and a beard - facial hair being a surefire warning sign in the '50s. (Remember the werewolf?) On the left side of the scale, ''All That Heaven Allows'' attacks suburbia by showing Jane Wyman framed in latticed windows with a prisonlike look.

Through this sort of analysis, Biskind identifies movies that feminize men, pit brains against brawn, test utopian ideals, celebrate the crowd, side with the loner, and push every kind of ideology the '50s had to offer. Along the way he probes the mental currents of the decade. Perhaps unwittingly, he also underlines a conservative slant among many of today's younger critics, whose leftish political views often don't jibe with their lavish praise for such right-leaning films as ''The Searchers'' and ''Invasion of the Body Snatchers.''

One trouble with ''Seeing Is Believing'' is Biskind's failure to address the relationship between movies and moviegoers. He doesn't distinguish the different audiences '50s films were aimed at: Fans of the teen-age werewolf were not the same folks who flocked to ''On the Waterfront'' and ''From Here to Eternity.'' Although he refers to it often, he doesn't point out that ''12 Angry Men'' was a flop in its day, however interesting it may look now. And he never proves that his arguments, illustrated by a relative handful of films, apply generally to Hollyood cinema of the '50s - a rich and varied body of work, though Biskind's breezy prose indicates a rather offhand attitude toward it.

Also puzzling is his decision to treat films in isolation from their makers, as if ''All That Heaven Allows'' did not reflect the special sensibility of Douglas Sirk as well as the soap-opera format he often used. Biskind grants that ''particular directors are often able to put their stamp on their work,'' but says ''these are exceptions'' - and then uses films by these ''exceptions'' to prove important points.

Finally, the author rarely follows his own correct precept that ''even the most apparently innocent aspects of script and casting, costumes and camera angle, are charged with meaning.'' If that's so, he might have focused on such matters more often and directly, instead of dealing mainly with plot outlines and character sketches.

Back on the plus side, Biskind has a healthy appreciation for the kitsch as well as the culture of movies, and a sharp eye for images, as the book's expressive photos attest. Despite its limitations, ''Seeing Is Believing'' is a helpful addition to '50s film criticism. And it will be a long time before anyone comes up with a better dust jacket.