''Wise Virgin'' is the sixth novel produced so far by a remarkable English writer in his early 30s. Its title derives from the biblical parable (in the book of Matthew) of the wise and foolish virgins: those who trimmed their lamps and were ready for a marriage ceremony, and those who whiled away the time without making the needed preparations. And, by the time this book's trim and elegant plot has run its course, Wilson's characters - and his readers - have received a comic and serious ''instruction'' on how to live in the world and how to make the best of one's imperfect nature. It is thus a comedy about the most serious matters imaginable, and a nimble entertainment that keeps on resonating in your head long after you've finished reading it.
Its hero, Giles Fox, is a middle-aged medieval scholar, who has been twice widowed and is blind. Disappointments have long been Giles's lot; in his youth he was denied a Cambridge fellowship, and the result of all these losses is a ''contemptuous attitude toward life'' that manifests itself in a well-practiced, coldly ironic manner. All that seems left for him to do is complete his edition of a 13th-century manuscript offering moral instruction to nuns, ''The Tretis of Loue Heuenliche''; it is ''a book seriously devoted to the notion that sex was evil,'' and it has - as Giles realizes only too well - cruel relevance for his own sobered and limited life.
The only other thing in Giles's life that isn't an object of his scorn is his daughter, Tibba, a 17-year-old beauty, who has essentially sacrificed her youth to play dutiful daughter to this inglorious ''if not exactly mute'' Milton - or, as she herself comes to imagine it, Cordelia to Giles's pathetic Lear. The chaste, bookish Tibba cooks and cleans her father's London house and spends her evenings reading to him from the novels of Sir Walter Scott; she scarcely seems aware that ''she was . . . living the life of the grown-up married woman while having to perform the tasks and rigours of the schoolgirl.''
Then, suddenly and drastically, each one's life is threatened by change. During a weekend spent with relatives, Tibba falls under the spell of a sophisticated schoolboy, one Piers Peverill - a notorious rule-breaker and troublemaker, who takes her for a spin in his MG and introduces her to excitements far more heady than the books she's given herself to. Meanwhile, Giles must deal with the entreaties of his research assistant, Louise Agar, a young spinster-scholar who decides she must devote her life to Giles's welfare and passionately demands that he marry her.
The plot of ''Wise Virgin'' is a glorious thing to behold: a seamless deployment of present scene and past summary in which every minor occurrence has the effect of bringing these people together and crucially altering their relationships with one another.
We know from the beginning - the long opening chapter which details the background of Giles's and Tibba's life - that we're in the hands of a novelist who knows his business. And, besides continuing evidence of Wilson's verbal and satirical skills, we're treated to such elegant pleasures as his droll capsule history of the survival down through the centuries of that medieval manuscript and his virtuosic use of parallelism - counterpointing Giles's amatory confusions against stern excerpted injunctions from the ''Tretis,'' and also balancing Giles's slow emergence from his shell of self-regard with Tibba's gradually more willing exchange of innocence for experience. These delicious conflicts climax with a Christmas Day visit that's a complete surprise and offers a totally believable and satisfying happy ending.
Yet, admirable as it is, the plot is not the thing in this formidably skillful book. hat keeps us engrossed is the depth and range of its characterizations. We see each of the important characters in terms of his and her feelings about all of the others, and the way these feelings keep changing is charted for us in revealing and moving detail. Louise Agar, for example, quickly comes to realize that, in her love for Giles, she has ignored the obvious difficulties and the differences between them and that she has mistaken his feelings for her (as she tells him, ''You like being adored, but you aren't in love''). The charming Tibba proceeds quite credibly from docile repression through a tentative discovery of the world outside her father's living room to a rapturous comprehension that love is ''more beautiful than anything in books could have prepared one for.''
Giles himself is a marvel of genuine mental complexity. Both his unpleasant egoism and his touching physical awkwardness are vividly described, as are the changes that slowly, surely, come over him. Realizing how Tibba has matured, and chagrined by his failure to give her room to breathe; able to perceive ''moral beauty'' in the dumpy, unhappy Louise; willing, even, to reconsider his irreligious iconoclasm and arrogance - Giles changes before our eyes into a more thoughtful and compassionate man than we would have believed him capable ofbecoming. That is almost as much of an achievement in a novel as it is in life.
A. N. Wilson has been compared to Evelyn Waugh, Angus Wilson, and other masters of serious farce. Such comparisons certainly hold, but I'd say that his emphasis on his characters' psychological and moral growth also links him closely with such analytical comic writers as Iris Murdoch and Joyce Cary. What's beyond argument is that he is one of the best English novelists at work today. I hope that more of him will soon be available to American readers.