THE MOURNFUL DEMEANOUR OF LIEUTENANT BORUVKA By Josef Skvorecky Translated from the Czech by Rosemary Kavan, Kaca Polackova and George Theiner Norton. 288 pp. $15.95

Bubble-shaped, topped with a foolish tuft of hair, impossibly shy when he's not on a case, Lieutenant Josef Boruvka of the criminal investigation squad of the Czech police department in Prague seems at first glance a sorry addition to the long list of fictional crime stoppers. But beneath his unprepossessing appearance are combined the logic of an Aristotle and the tenacity of a bulldog.

Making his first appearance in English with these 12 stories, Bubble, as he is known to his disrespectful colleagues, proves himself more than a match for any criminal. Normally good-tempered, he becomes mournful only in success. Crime upsets him, and proof of murder makes him sad. The closer he comes to the solution of a case, the more melancholy becomes his expression, until by the end of each story he seems poised on the brink of tears.

There is something oddly antique about short detective stories. They smack of the 19th century. A mystery novel has room to move and develop. It can become a serious commentary on the society in which it occurs, while its hero -- like Raymond Chandler's Philip Marlowe or Dashiell Hammett's Sam Spade -- may be as complex and interesting as any character in serious fiction. But the short detective story is more like an anecdote. It rarely has any emotional level. One hardly cares about the characters or the crime, and the weakness of such stories is that they are often too mechanical -- they become intricate but not very interesting little machines. Reading them is like eating salted nuts. When they work -- like the Sherlock Holmes stories -- it is usually because of the cleverness of the puzzle and its solution, because of the personality of the detective, and because of the level of the writing and the imaginative skill of the author.

Most of the stories in "The Mournful Demeanour of Lieutenant Boruvka" work very well, even though they are intellectually rather than emotionally engaging. One enjoys their wit. Author Josef Skvorecky is very fond of locked-room mysteries, and again and again Boruvka finds the key to a seemingly perfect crime -- a murder on a pinnacle of rock far away from anybody, a murder in a shower in a theatrical dressing room surrounded by people, a murder in a cable car where the victim was apparently alone hundreds of feet above the ground.

Boruvka himself is an attractive and amusing character both on the job and away, as we see him dealing with his stubborn and voluptuous daughter Zuzana and being tempted by the chance of romance with a particularly pretty female police officer. Finally, not only are the stories well written, but they are constantly witty and engaging. Skvorecky, who emigrated to Canada from Czechoslovakia in 1968 and is now professor of English at the University of Toronto, is the author of more than half a dozen novels available in English, including "Dvorak in Love" and "The Engineer of Human Souls."

The weakness of the stories is often their artificiality -- the murderers tend to commit their crimes for the skimpiest of reasons, and mechanics too often take precedence over people. Because of their absence of psychology, these stories are the very opposite of Simenon's featuring Inspector Maigret, while the characters, apart from Boruvka and a few others, tend to be one-dimensional. But in their turns and jokes and constant wit, the stories are often delightful. There is a certain pleasure in seeing an intelligent mind at play. Despite his mournful demeanour, Lieutenant Boruvka is a welcome addition to the canon. The reviewer is a poet and mystery novelist. His most recent book is "A Boat off the Coast.