Lonnie Coleman is the rare writer who can create for both the commercial and literary markets. His million-selling "Beulah Land" trilogy, a steamy saga of sex and slavery in the pre-Civil War south, is filled with explained instead of revealed characters and authorial manipulation that has the express purpose of titillating the senses. But he has also written several critical successful novels, including "Adam's Way," "Clara," "Orphane Jim" and now "Mark," books peopled with characters whose lives we can enter instead of simply observe voyeuristically.

"Mark" is the story of a boy, Mark Bowman, growing up in the 1930s, author Coleman's own growing-up time, which gives the Depression South setting an anchor in realistic detail. It is an initiation novel, wherein a boy becomes a man, gaining the material for a life's work as a writer and a sexual self. Orphaned at 13, Mark is taken in by his aunt and uncle who live in Montgomery, Ala., with their two children, Roland, 17, and Beatrice, 16. Although money is not plentiful, food is: Uncle Grady is a food broker.

Mark is already a mature young man when he begins life in his foster family. He goes to work in his uncle's warehouse and with the money he earns offers to pay room and board. He grows closer to Uncle Grady and Cousin Beatrice. He makes a friend at school, Marshall Blake, and he shows his first poetry to his English teacher who considers him promising.

There is a certain attractive arrogance in Mark, the poet, and Marshall, the actor. Each expects to be Somebody when he grows up: "All our work was yet to do, but we knew surely that it would come, be done, be good; and all the world would celebrate our triumphs and strive to touch us, hold us, love us."

In fact, by the time the book closes, Mark is on his way to the success he predicted. Only difficulties over money seem to stand in his way. Mark wishes to attend the University of Alabama when he finishes high school, but the only money he can raise is through a student job. His high school mentor and friend, the finely drawn Margaret Torrence, steps in to help. Later, when Mark loses his student job, a new acquaintance named Carl, a scholarship athlete who admires artists, rescues him. Things have a way of working out for Mark. What could have been the cutting edge of this novel is dulled by things always working out.

Throughout the novel, Mark and Marshall fall in and out of love, talk sex and imagine future conquests. Mark earns $27 the summer before he goes to college by letting a homosexual touch him. On the last night of this activity, Mark tells the man, "Hope you don't mind my saying I'm glad I'm not queer." The honesty of the remark echoes later in the reader's mind.

At the university, Marshall begins intimate involvement with women, but Mark fails to find the right opportunity. Before long, Mark decides that the time has come to face a question that has been growing in his mind. He tells us, "Folklore said that the obvious remedy was to go to the right woman." We are convinced that Mark wishes once and for all to lose his virginity. He alerts Buffie Weatherhead, the sympathetic wife of a college professor, telling her that he has begun to doubt his masculinity. He is serious, although at the time we don't realize in what way. The author has failed to prime us with what is going on in Mark's mind. The coupling proves satisfactory, although Mrs. Weatherhead is dirty and has prickly hairs growing between her breasts.

Mark returns to his dormitory room to find Carl, and before long they are in bed together. Mark's questioning resolves itself: He is homosexual. Surprisingly, given 1940s attitudes toward homosexuality, he does not struggle with this new knowledge. The unprepared reader does. The love affair with Carl flourishes until the advent of World War II separates them. It is left only for Mark to establish himself in the literary world, which happens when he wins first prize in both the Mademoiselle and Atlantic Monthly young writers contests.

"Mark" is most valuable for its fine characterizations, especially that of its title character, who remains sympathetic primarily due to the kindly first-person narrative that the author carefully sustains. But none of his characters fails to spring wholly to life. Take, for example, Margaret Torrene:

"Past forty now, Miss Torrence was careless of her person in a way that no one who admired her considered important. A shoulder strap of her slip might have broken and been pinned instead of mended. She wore no cosmetic except face powder, and that only when she thought of it, usually applying so much absently that her face was like a clown's mask, emphasizing the stark, intense eyes which could be as disconcerting as an owl's. . . . She talked of politics as if it was a normal interest, not part of a subject called civics."

Where "Mark" fails is in a vitality diminished because the two things Mark wants most come too easily to him. The opportunity was there: His writing success could have been more hard-won or he could have engaged in a real struggle over his homosexuality. But both are givens, something that this reader finds hard to believe.