BOOKSTORE BROWSERS well over 40 will probably be the first to shout "Cushlamochree!" when they spot these first volumes of Ballantine/Del Rey's projected complete reprint of Crockett Johnson's great comic strip, Barnaby. But younger people should catch on quickly, and they are in for a treat, because the unique world Johnson created for Barnaby has survived the years intact. From the outset of its 10-year run (1942-1952), Barnaby attracted the same kind of cult following that George Herriman's Krazy Kat had enjoyed since the teens and Walt Kelly's Pogo was to attract later.

Sophisticates like Robert Nathan, Louis Untermeyer and Dorothy Parker followed the strip avidly and made ecstatic pronouncements; Volume 4 of the present series opens with a letter from Dorothy Parker to the New York tabloid PM, where Barnaby originally appeared, in which she writes, "I think, and I am trying to write calmly, that Barnaby and his friends and oppressors are the most important additions to American arts and letters in Lord knows how many years. I know that they are the most important additions to my heart." A friend who was working in a nest of Manhattan Barnaby addicts at the time compares their fervor to that now aroused in fans by Doonesbury when he's on to something hot.

Considering the passionate tone of those endorsements and the turbulence of the times in which Barnaby came into being, the gentleness of the strip itself will surprise those who are coming to it for the first time. Johnson's drawing style, which incorporates simple outlined figures placed against flat backgrounds with a minimum of detail and with the often crowded voice balloons set in type rather than hand-printed, certainly lacks the surrealist zap of Krazy Kat or the wild political orthography of Pogo, but read on.

It is perfectly in tune with Johnson's basically simple story: Barnaby, a bright and articulate little boy of about 5, wishes for a fairy godmother as he lies in bed after listening to his mother read him a fairy tale. Suddenly the story seems to be coming true. A "bright star" shines outside of his window just as it had in the tale, but instead of a fairy godmother there appears the cigar-smoking Jackeen J. O'Malley, a 2-foot-11 pixie with pink wings who will become his grandiloquent and ambitious but completely incompetent fairy godfather, and whose expletive of choice, "Cushlamochree!," peppers Barnaby the way Charley Brown's "Good Grief!" does Peanuts. As Mr. O'Malley leaves through the windows, he fails to become airborne and crashes into the rose garden.

When Barnaby's parents come into his room to find out why he's still up, he tells them about his new fairy godfather, but they explain that he's been dreaming and that he should go back to sleep. But when the unconvinced Barnaby gets up to look for evidence, he finds cigar ashes.

From this point on, one of the ongoing jokes of the story is Barnaby's inability to convince his parents of Mr. O'Malley's existence. In the 10 years that follow he is also unable to produce for them any of the many other supernatural types Mr. O'Malley brings onto the scene: a meek, highly literate and easily frightened ghost named Gus; the talking dog Gorgon, who refuses to utter a syllable when Barnaby's parents are around, but who is a crashing bore when he does speak; an uncouth leprechaun named McSnoyd who speaks with a Bronx accent; Atlas, the slide-rule carrying mental giant; Davy Jones, the King of the Sea, who casually hands Barnaby some pieces of eight for his piggy bank, thereby triggering a frantic treasure hunt by vacationers who tear up the beach looking for more; and many others, all of them notable for utter ineffectiveness when it comes to using their supernatural powers.

THIS SOUNDS like a rather thin and whimsical premise, but Johnson gives it substance with smart dialogue and plot tangents that bear sharp political barbs. In the early episodes of Wanted: A Fairy Godfather, which appeared during the war, most of these have to do with German espionage. In one episode, while walking in the woods Barnaby and Mr. O'Malley come upon a parrot that keeps repeating remarks like, "For dis voik, Fritz, it gifs medals from der Fuehrer! Vendsday at eighdt sharp we blow oop der powerhowz." Barnaby alerts the police and the day is saved. Later, in volume two, Mr. O'Malley and the Haunted House Barnaby and Mr. O'Malley visit the old abandoned house from which the terrified Gus the ghost has been driven by strange noises. There they find the "hot coffee ring," a gang of thugs who hijack coffee shipments and store the beans in the basement of the house. Once again justice is done, although Barnaby's explanation of how he caught the ring is attributed to his overactive imagination.

Reading Barnaby end to end by the volume does point up shortcomings. The failure of his parents even to suspect that there may be something funny going on in the house becomes exasperating, especially as they are otherwise among the most intelligent and enlightened parents in any comic strip. But one accepts it. Anyone who responds to Barnaby enough to finish the first volume and go out to buy the second will be so grateful for its warmth and intelligence that he will be happy to overlook its rare absurdities and inconsistencies. The blurb provided by the publisher states that before Crockett Johnson, whose real name was David Johnson Leisk, became a cartoonist he had a job with Macy's advertising department from which he was fired "for wearing a soft collar instead of the regulation stiff one," and this portrait-by-anecdote seems about right.

The republication was the brainchild of Judy-Lynn Del Rey, whose recent death prevented her from seeing the project through to its completion. New generations of Barnaby-ophiles will be grateful to her.