Perfect end for a worthy series; The Killing Ground, by Mary Lee Settle. New York: Farrar, Straus & Giroux Inc. 364 pp. $14.95.

The appearance of this fifth and final volume of Mary Lee Settle's ''Beulah Quintet'' is a literary event of some importance -- though many readers of serious fiction may not realize this. For, sad to say, little attention has been paid to Settle's chronicle of peculiarly American crises and challenges, successes and failures.

The novels before this one have dealt with the intermingled fortunes of several ambitious, energetic, variously troubled, and compromised families. ''O Beulah Land'' (1956) describes the settlement of what will become West Virginia, and introduces us to the forefathers whose descendants' lives are examined in succeeding stories. ''Prisons'' (1973) looks backward to 17th-century England and the history of religious persecution. ''Know Nothing'' (1960) uses the background of the developing Civil War to depict intimate allies caught up in burgeoning discord. ''The Scapegoat'' (1980) brings the tale to this century, employing a coal strike in West Virginia in 1912 to show how these related people continue to oppose and oppress one another.

Now, in ''The Killing Ground,'' we reach the present day. Novelist Hannah McCarkle, descendant and namesake of the heroine of ''O Beulah Land,'' is presented to us as author of Mary Lee Settle's own novels. She returns in 1978 to her West Virginia hometown after ''eighteen years of work, poverty, and exile'' on various liberal-intellectual fronts. Her ironical, questioning fictional portrayals of her background and family have made her as much renegade as stranger. An invitation, nevertheless, to lecture rekindles Hannah's contempt for her posturing, self-deluding ''proper'' old friends.

Then, news of a suicide -- a popular local bachelor and gadabout -- brings to the forefront of Hannah's consciousness her ever-present memories of her brother Johnny, who was killed during a fight in a jail cell 18 years earlier. She realizes anew what the burden of her life's work has been, and again acknowledges her need ''to find him, bless him, release him, and bury him at last.''

The novel thus meanders through numerous past and present scenes, as Hannah gradually comprehends the tangle of conflicts which underlie her brother's death and achieves a recognition of the insensitivity and injustice on which the McCarkles' wealth and privilege were built.

''The Killing Ground' is weakened by Hannah's/Settle's uncompromisingly sardonic mockery of her people's values. At its best, though, this darkly powerful saga, reminiscent of some of Faulkner's best work, compels us by virtue alone of its keen understanding of the ironical shaping power of history. When the one man whose words we expect her to scorn tells her ''Oh, Hannar, honey, they's things in the past you can't do nuthin' about'' - and Hannah accepts this as the culmination to her searching - well, it's the moment that all five volumes have shaped themselves toward, and it is beyond praise. Suffice it to say that the Beulah Quintet is a major contemporary work, and ''The Killing Ground'' brings it to a splendidly satisfying conclusion.