'The Bostonians': so far, the best movie of the year. Merchant; Ivory, Jhabvala (and Henry James) have done it again

Summer is always a silly season at the movies, deluging us with fantasy and farce. This year is no exception, as ''Ghostbusters'' and ''Gremlins'' set the pace.

But a few serious offerings have sneaked in through the back door. The latest is ''The Bostonians,'' taken from Henry James's novel. It joins ''Under the Volcano'' in showing that literary adaptations are still a thriving enterprise for film - and that they needn't be washed out like ''The Natural,'' which kicked off the current spate of page-to-screen translations.

To say it right out, ''The Bostonians'' is the best movie I've seen all year. The story doesn't exactly gallop along - this is Henry James, after all - but it canters with an easy, flowing grace. Add a long list of vivid characters, and a mood as rich and proud as old Boston itself, and you have a hearty entertainment that's as thoughtful and engaging (if not so deep or imposing) as its source.

And talk about timely! The background of the novel, published in 1886, is the struggle for women's liberation, a subject James explores with great energy, if not as much insight as present-day readers might wish. Both the film and the book keep personal drama in the forefront, focusing on characters more than issues. But those issues lend the tale an extra fascination, and the filmmakers make good use of them.

The central character is Verena Tarrant, a young feminist with a talent for public speaking. Two other figures circle about her: a militant liberationist named Olive Chancellor, whose dedication borders on neurosis, and Basil Ransom, a suitor from Mississippi who thinks a lifetime of quiet housewifery is all a real lady could want. Beginning in 1875, not long after the Civil War, the story traces a struggle between intense Olive and chivalrous Basil for the heart and loyalty of Verena, whose sincerity is equaled only by her indecisiveness.

It's a dramatic plot as James wrote it, leavened with amusing twists of character and wry observations by the narrator. The filmmakers stay surprisingly close to the novel, considering its length, but some changes are evident. The movie's first and last scenes concern the militant Olive, for instance, making her (not Verena) seem the central character. And because film is such a literal medium, some of the story's subtler undercurrents come into unexpectedly high relief. This particularly affects the repressed sexual dimension of the relationship between Verena and Olive, which seems more immediate on the screen than on the page, despite the film's impeccable tact in treating such matters.

The adapters have mostly avoided tinkering, though, even when it might have helped James's narrative seem still more relevant to current concerns. For one important example, James's bottom-line attitude toward feminism seems to be embodied in a character named Dr. Prance - a self-made woman physician whose professional and intellectual activities keep her too busy to fuss with movements or dabble in causes. Her attitude is understandable but not acceptable , I feel, because it denies the need for political as well as personal action when a society's well-being is at stake.

At first the filmmakers mitigate this a bit, making Dr. Prance seem impatient with the rhetoric rather than the goals of the movement. But eventually she admits her lack of sympathy with the whole struggle, a position that seems less benign today than it might have a century ago. Only at the end does the screenplay make its own perspective clear, allowing the passionately committed Olive to air her views in a speech instead of vaguely dismissing her as James does on the last page.

Credit for the cinematic excellence of ''The Bostonians'' goes directly to the team that made it: director James Ivory, screenwriter Ruth Prawer Jhabvala, and producer Ismail Merchant, who have worked together for more than 20 years. Henry James is an ideal author for their highly civilized sensibility, although even their delicate 1979 version of ''The Europeans'' didn't prepare me for the full-blown riches of their new effort. In filming ''The Bostonians'' they have caught not just the intellect and dignity of James, but his sardonic and satirical undertones as well - and yes, the vigor of his storytelling, which spurs this novel even when its prose waxes florid and indirect.

Next up for praise are the performers. Christopher Reeve, trading his Superman cape for a 19th-century model, is the soft-spoken but strong-willed Basil down to his toes. Vanessa Redgrave gives Olive a complexity that deepens and quickens her every scene. Madeleine Potter, a newcomer to the screen, captures Verena's essence, though her mannerisms are a trifle cute.

And the supporting cast is a major delight in itself. Linda Hunt, fresh from ''The Year of Living Dangerously,'' brings Dr. Prance to vivid life in a few brief scenes. Jessica Tandy does the same with Miss Birdseye, an aging veteran of the liberation movement. Wesley Addy breathes a sly wit into his portrayal of Verena's ridiculous father, a ''mesmeric healer'' with very dubious motives. And it was a brilliant stroke to fill the role of newshound Matthias Pardon with the most unactorish of actors, Wallace Shawn.

I have a few gripes about ''The Bostonians.'' The early scenes are too heavy with exposition; there's too much melodrama in a Cape Cod scene when Olive worries about Verena's safety; the last moments with Verena don't have the poignancy of James's account. But these are minor points when taken in context. Most of the way, starting with the spectacular organ recital under the credits, this is an exhilarating picture.

'Best Defense'

There must be room for a humorous perspective on the arms race, but the movies haven't found it yet, even though experienced filmmakers like William Friedkin and Richard Brooks have tried.

The latest effort comes from director Willard Huyck and producer Gloria Katz, who co-wrote the screenplay of ''Best Defense'' and enlisted Dudley Moore to play the lead. Also on hand - candidly labeled the ''strategic guest star'' - is Eddie Murphy, although his path never crosses Moore's for a minute.

Moore plays a lazy engineer who is about to be fired from yet another job with yet another defense contractor, because the firm can't solve a technical snag it's facing. In an old-fashioned story twist, our hero gets the solution from someone else, then pawns it off as his own. The scenes with Murphy take place two years later, as he wrestles with a piece of military equipment that incorporates this brainstorm. Subplots involve an extramarital fling and a black-market arms merchant, among other things.

Katz and Huyck, whose writing credits include ''Indiana Jones and the Temple of Doom,'' come up with a few funny situations, mostly involving the manic black-marketeer inventively played by David Rasche. Kate Capshaw has some good moments as Moore's long-suffering wife, and George Dzundza is solid as his conniving pal. But the filmmakers fall back too easily on simple coarseness when better ideas don't come to mind, and they expect us to giggle at four-letterisms that lost their shock value long ago. Moore and Murphy deserve stronger vehicles.