Flann O'Brien (At Swim-Two-Birds, The Hard Life, The Poor Mouth) is coming into his own. So high is his stock that his publishers can pull together a collection of this-and-thats--a wee taste of an unfinished novel, two stories, two plays, and an appreciation of his countryman with the very long shadow, James Joyce--only to be met with delight. Claud Cockburn in the introduction wonders aloud if the Irish Times column O'Brien wrote under the pseudonym Myles na Gopaleen might not have drawn off some of the energy that rightfully belonged to novelist O'Brien (whose real name--not to confuse--was Brian O'Nolan). But, on the other hand, maybe the same situation accounts for the immediacy and brisk, self-contained wit that makes a fragment of O'Brien the next best thing to the whole pie. (Pick any line: ""James Joyce was an artist. He has said so himself. His was a case of Ars gratia Artist,"" etc.) The unfinished novel Slattery's Sago Saga was to be the account of how a Scots-American millionairess enacts her plan to rid the U.S. of the lazy, good-for-nothing Irish scum by rooting up the potato and replanting Ireland with a no-fail starch-producing tropical tree called the sago. The stories are aesthetic refinements of the barroom tall tale; and in ""Faustus Kelly,"" a three-act play, the devil himself is utterly destroyed by the moils of corrupt Irish politics. Chauvinism is the subject--perversity is the mode. ""With laughs he palliates the sense of doom that is the heritage of the Irish Catholic"": that's what he says about Ireland's other comic genius--but it applies here as well.