STARTING OUT IN THE EVENING.<i> By Brian Morton</i> .<i> Crown: 336 pp., $25</i>

The characters in Brian Morton’s “Starting Out in the Evening” spend so much of their time (and ours) in the act of thinking--considering and reconsidering, analyzing and reflecting--that the habit of rumination rapidly proves contagious. Even the most shallow souls may find themselves reading with part of their minds on the novel and the rest turned inward, monitoring their own reactions. This mental tracking back and forth is, of course, part of the process of reading, but something about this novel makes one conscious of its mechanics, the way that watching someone with a tic can make us aware of blinking.

Morton has cast his quiet drama with a small, tight ensemble of decent, sensitive, more or less highly evolved men and women. At the apex of an unusual emotional triangle is an ailing, elderly writer named Leonard Schiller, the author of several highly praised novels. Of late (in recent decades, that is), his star has cooled and faded, along with the whole galaxy of which he was once a part, the New York intellectual scene of critics and writers, big thinkers and big talkers: “Kazin and Howe and Trilling and Rahv,” “children of immigrant parents, children of the Depression, mad for writing--in all these ways, they were members of the same tribe.”

As Schiller struggles to conserve what little remains of his physical and intellectual powers, his energies are at once buoyed and taxed by the scholarly interest and adoring attention that he seems to have inspired in an attractive young woman named Heather. A graduate student at Brown, Heather believes that she owes her passion for literature--and her ideas about the world--to an accidental, youthful and life-changing encounter with Schiller’s early novels. Now she aims to repay this debt (and jump-start her academic career) by writing her thesis on Schiller, by making herself personally indispensable to the overweight survivor of two heart attacks and by offering him one last shot at literary immortality.

What ensues is a romance of sorts, far more intellectual than amorous, and all of it monitored with curiosity, possessiveness and mild alarm by the novel’s third main character, Schiller’s daughter, Ariel. A former dancer, still hoping for a husband and children as she drifts into her late 30s, Ariel is a recognizable boho sort: a good-hearted, childlike woman who has indulged in serial flirtations with “Buddhism, Hinduism, Taoism, yoga, tai chi, Codependents Anonymous, Rolfing, Authentic Movement and the Alexander Technique.”

Early in the novel, Schiller explains his method of composition--and we can’t help suspecting that Morton is describing his own approach to plot construction: “You just sit down at the typewriter and follow the character around. . . . You write page after page after page just finding out who they are. You wait for them to do something interesting.” Morton follows his characters to coffee shops and museums, stuffy Uptown apartments and smoke-filled Downtown clubs, to hospital rooms and bedrooms. And plenty happens along the way. There’s lovemaking of sorts, suffused with a tender purity we haven’t seen the likes of since Tristram and Isolde spent the night with a sword between them. There’s illness, death, a rekindled love affair--really, enough for several novels.

Still, we’re always aware that Morton is less interested in what his characters are doing than in what they’re thinking. In fact, no matter what they seem to be doing, what they’re really doing is thinking about themselves, their relations with each other, art, literature, history, moral seriousness, love, God, immortality. Here’s what goes through Schiller’s mind “between the bus stop on Lexington and the bus stop on Park,” as a consequence of seeing a man in a stupid T-shirt:

“The primary human need, he decided--stronger than the need for food or sex or love--is the need for recognition, the need to make a mark in the world. One makes one’s mark according to one’s capacities. If you have talents, you exercise them: If you’re Mozart, you write ‘The Magic Flute.’ And if you don’t have any talents . . . you wear stupid T-shirts.”

This is a world in which no one ever has to ask which James brothers you mean, a world in which a terminally ill patient spends his last days reading Leon Edel’s biography of Henry and another man--in the midst of what he fears is a heart attack--comforts himself with a remembered anecdote about William facing death. There’s nothing lightweight or trivial about these characters, but also, as should be apparent by now, they’re not a whole lot of fun. After a while, we may find ourselves gasping for air and feeling that too many of these musings border on the banal. (“So much of human life is animal life: we respond to each other as animals.”)

Occasionally, Morton defuses our resistance by letting characters express the reservations that we may be guiltily harboring. When Ariel asserts that “without struggle there’s no life,” her father wishes she were less susceptible to the lure of pop psychology. And Ariel identifies--for us--Heather’s every fault, from her self-satisfaction to the commonness of her name. Yet still we’re meant to admire the complex humanity of these people and to applaud their search for happiness, success, immortality or whatever. It does make one reflect about the best way for philosophy to make its way into fiction how much more graceful and less off-putting it is to give a weighty idea to a shady or ironic character. (One thinks, for example, of the brilliant sermon on pleasure versus Puritanism, celebration versus criticism delivered by the problematic narrator at the end of John Cheever’s “Goodbye, My Brother.”)

Morton’s achievement--and failure--is to have created characters so utterly lifelike that they strike us as being precisely like certain people we know. And our response to the novel reflects our feelings about these familiar types: so touching and so humorless, so admirable and so maddening, as they simultaneously tug on our heartstrings and grate lightly on our nerves.