The Blossom Quartet Ends : A BLOSSOM PROMISE <i> by Betsy Byars; illustrated by Jacqueline Rogers (Delacorte Press: $13.95; 145 pp.; ages 9-12) </i>

In 1970, Betsy Byars won the Newbery Medal for “Summer of the Swans,” a novel rich with the conflicting emotions an adolescent girl feels for herself and her retarded brother. After the boy is lost in the woods, his sister realizes how important they are to each other. In “A Blossom Promise,” Byars again uses a near-tragedy to draw characters to one another as they grope for understanding. Her perception of kids’ feelings is keen, as is her wit and eye for detail.

This is the final, bittersweet volume in the Blossom Family Quartet, bittersweet only because the cast is so memorably quirky that you hate to say goodby. Those who aren’t familiar with the earlier episodes might be teased into reading them after references to Ralphie’s jail time and the Green Phantom. Meanwhile, three subplots weave together: Vern and his friend, Michael, plan to float their rickety raft down a rain-swollen river, Junior plans to spend the night in Mad Mary’s Cave, and Maggie and her mother ride the rodeo circuit in Arizona.

At first it’s hard to tell how any of this relates to the next, but Byars skillfully ropes it all in. Pap’s heart attack as he tries to rescue the rafters is the catalyst that kicks the Blossoms’ spirit into high gear and shows their love for one another. There are enough cliffhangers and moments of despair that when all ends happily, you want to applaud. There’s no sap.

One problem: Though it’s been said you can’t judge a book by its cover, young readers do--that front illustration is usually what entices them in the first place, so what a shame for them to miss a terrific story because of a blah picture. Unfortunately, ‘tis the case with the cover of “A Blossom Promise.” It shows three kids sitting around the table looking at photos, with another girl bending over them. They’re smiling gaily and are dressed for success rather than the down-home style of the story. There’s no hint of the plot’s adventure or tension, plus the young (she looks 14) girl standing up turns out to be the mother , from a scene in the last pages. Jacqueline Rogers’ inside drawings are fine black and whites that do reflect the dramatic range; the publisher should have chosen one of those instead. Cover aside, Blossom Family fans will probably race straight to Chapter 1. Let’s hope newcomers do the same.

THE CHALK BOX KID by Clyde R. Bulla; illustrated by Thomas B. Allen (Random House: $1.95, paperback; 59 pp.; ages 8-10).

Los Angeles author and master storyteller (“Viking Adventure,” “White Bird,” “John Billington, Friend of Squanto”) gives us yet another protagonist that kids will cheer for. Gregory’s 9th birthday is the worst ever: His father has switched jobs; they’ve moved to a shabby neighborhood, and Gregory feels friendless in his new school. Then one day while exploring an abandoned chalk factory, he discovers two boxes of chalk in a room blackened by fire. On the walls he draws a garden so beautiful that his loneliness is transformed and a special friendship results. Bulla’s simple, clean style is easy to read, and he proves once again that he understands children. Charcoal drawings by Thomas B. Allen (“In Coal Country”) are lovely.