This is Anthony Burgess' shortest book. But he manages within 76 pages of prose deftly to expose the holy and the unholy parts of man, and to describe how they might mingle to make a modern philosophy.

Burgess conjectures a meeting between two remarkable poets in the winter of 1820 -- the dying John Keats and the conscience-troubled Giuseppe Belli. Both poets were tortured by love, and Burgess uses the evidence of their sonnets to construct a bawdy and touching Roman tale. While sticking to the historical facts of the two poets' lives, he gives us a sense of the artists as living people. We meet them in the literary locker room, so to speak, where the poets hang up their Grundies and tell triple-meaning jokes about the Roman word for penis. Keats, atheistical but full of faith (in love, at least), discovers Belli's ribald sonnets which are written in the Roman street dialect.Belli, split by passion and piety, is led eventually by the influence of Keats to write more sacrilegious verses during the lunch break from his job as papal censor.

The subject of this little book is religion, but it is characteristic of Burgess, and of his two poets, that in discussing God he was able to catalog a dozen words for penis and a score for testicles. Burgess finds in Keats' faith and Belli's coarse poems a compound of blasphemy and belief that is a good tonic for his, and our own, pessimism about the modern world. Burgess suggests, finally, that we might distract ourselves as Keats did while he was waiting to die in Rome. Speaking through Keats' friend, the pious Joseph Severn, Burgess says:

"'If blaspheming makes you more cheerful, then I suppose you must blaspheme,' Severn said stoically. 'But I wish there were some other way of making you cheerful.'" Keats and Belli go on blaspheming cheerfully, and the book's fictional narrative is followed by 71 of Belli's sonnets, newly translated. (Little Borwn, paperback, $4.95)