BOOKS OF THE TIMES

IRONWEED. By William Kennedy. 227 pages. Viking. $14.75.

''IRONWEED'' is William Kennedy's fourth published novel and the third in his series set in Albany, where he lives and teaches (at the State University of New York), and which he obviously knows as well as he does his own nightmares.

''Ironweed'' - which refers to a tough-stemmed member of the sunflower family - recounts a few days in the life of an Albany skid-row bum, a former major-league third baseman with a talent for running, particularly running away, although his ambition now, at the height of the Depression, has been scaled down to the task of getting through the next 20 mintues or so.

The novel is rich in plot and dramatic tension, building as it eventually does, to a violent showdown between a gang of marauding American Legionnaires and a handful of derelicts in a hobo jungle. It is almost Joycean in the variety of rhetoric it uses to evoke the texture and sociology of Albany in the 1930's, particularly the city's Irish community, which by the time of the novel is in full control of the city's politics. And the book is remarkable in its refusal either to sentimentalize or trivialize ''life on the bum.''

Francis Phelan, the down-and-out protagonist, has plenty of reason for being a bum. Many years earlier, as an employee of an Albany trolley line out on strike, Francis threw a stone at a strikebreaker and fatally cracked his skull, which forced him to run away from Albany for a while. Only a few years later, he picked up his 13-dayold son by the diaper - as he had often done with his two older children - only to have a safety-pin snap open and the infant fall to the floor and die of a broken neck. This led Francis to run from his family for good. Ever since, he has been doomed to kill, just as he is at the climax of ''Ironweed.''

Yet Francis's guilt over these misdeeds doesn't really account for his self-contempt and sense of having erred, which are of sufficient magnitude to universalize him as a human being doomed to sin. And conversely, no matter how low Francis sinks - no matter how drunk and foul smelling and abhorrent to the eye he becomes - Mr. Kennedy continues to grant him access to the spontaneous ecstasy that being alive entitles him to.

Here is Francis falling asleep on a freezing night in a deserted barn. ''The new and frigid air of November lay on Francis like a blanket of glass. Its weight rendered him motionless and brought peace to his body, and the stillness brought cessation of anguish to his brain. In a dream he was only just beginning to enter, horns and mountains rose up out of the earth, the horns - ethereal trumpets - sounding with a virtuosity equal to the perilousness of crags and cornices of the mountainous pathways. Francis recognized the song the trumpets played and he floated with its urgency, he ascended bodily into the exalted reaches of the world where the song had been composed so long ago. And he slept.