Carkeet has followed his fine and funny baseball novel, The Greatest Slump of All Time, with an adept, enjoyable academic/literary fantasy revolving around Mark Twain. Along with Halley's Comet in November 1985 arrives Sam Clemens, dropped in for another short (as long as comet stays: 7 months) go-around, first stop: Nevada. The book proposes a sprightly manuscript Clemens writes about this baffling-to-him return--""I Been There Before""--that details his travels to a variety of spots: California, the Mark Twain Archives at Berkeley, New Orleans, Hannibal, New York, Hartford, Elmira--all beautifully limned in mock-Twain. This manuscript, episodic and delightful and learned and very amusing, is the highlight of the book. Academia comes in for tweaking as well, though, as the Twain scholars scramble to regroup once they realize (the ones who even allow themselves to) that Twain, in fact, is back. Subtly and not, Carkeet lampoons the pieties and the politics of literary canon-making (and the elements of hucksterism in it all); yet a touch of detective story--tracking down Twain, known only by the fragments of manuscript he keeps depositing--extends a point or two to real scholarship as well. While not the sort of book that's got an especial undertow, that you'd read first to last in the least possible time, Carkett's novel has all the elements--intelligence, comic charm, satiric specificity--to make it an entertainment of a high-spirited order.