By Margaret Truman

Random House. 293 pp. $18.95END NOTES

How apt -- what some might irreverently call a stroke of amazing grace -- that in this year of our Lord 1990, the year in which the Cathedral of Sts. Peter and Paul has been completed, Margaret Truman would contribute to the yearlong celebration by publishing "Murder at the National Cathedral." Cathedral planners and readers of Truman's capital crime series will not be disappointed with this, her 10th suspense novel. All the bodies and blood, sex and surprise, intrigue and excitement Truman has given readers in the past are here again, this time melodramatically illuminated against a Gothic backdrop of stone and stained glass.

Back for a return engagement are the stars of "Murder at the Kennedy Center," the impeccably handsome, dashing and intelligent MacKenzie Smith and the gorgeous Rita Hayworth look-alike, Annabel Reed. In the first few pages they are married in -- of course -- the Washington Cathedral. They are once again partners in avocational sleuthing.

What Truman does best is to tell a vigorous tale of twists and turns. Her plot is knotted with enough terror and fearful intimations that a bestseller is guaranteed. After the body is discovered in the cathedral, the novel's energy rises, and questions are as numerous as candelabra.

What is the motive? Where is the murder weapon? Has the body been moved? Who is the murderer? Is it the puritanical, emotionally crippled, gargoyle-like Father Jonathan Merle? The stunningly beautiful Rev. Carolyn Armstrong? The jealous, angry choir director, Wilfred Nickelson? Bishop George St. James himself, so concerned with avoiding scandal and shielding his clergy? A CIA agent? A British intelligence operative? The Navy? The Mafia? Could it even be a Korean assassin who has infiltrated the suspicious Word of Peace Organization, of which the victim was a prime mover? Moreover, is the murder of a British priest in the Cotswolds connected with the cathedral corpse? Were both victims involved in illegal activities? For nearly 300 pages, these questions remain unanswered, and the reader sees through a glass darkly. Not until the very end does Truman skillfully disclose the identity of the killer, and does the cathedral return once again to being a "national house of prayer for all peoples," as Congress decreed in 1893.

What Truman does not do so well -- in fact, does barely well enough -- is to depict character. Mac and Annabel are cloyingly perfect, middle-aged yuppies: so stylishly banal that they are almost unbelievable.

Mac, a retired criminal lawyer now teaching law at George Washington University, knows all the important people, for whom he has done favors and, of course, by whom he is almost revered. Annabel manages a pre-Columbian art gallery in -- where else? -- Georgetown. They're fine when tracking down suspects; however, when relating as husband and wife, playing at marital banter, reflecting on life, they seem shallow. Here is Mac mooning over Annabel and debating whether he should inform her of the latest developments: He "looked into her large green eyes and had a sudden burst of recognition, which had been happening with some regularity since the wedding. They were married. She was his wife. No secrets. Right? Right!"

Other characters fare little better. Tony Buffolino, Mac's ex-policeman friend and aide, is loutish and awkwardly ethnic; chief of homicide Terrence Finnerty is merely an extra, with little purpose except to lend verisimilitude. The bishop is one-dimensional, worried only about funds and scandal. A few other misgivings: When a young choirboy makes a local telephone call to reveal significant information, he is told, "Deposit fifteen cents for an additional three minutes." Would the C&P Telephone Co. extract such an extra charge? And why, some readers might wonder, does nearly every chapter begin with a weather report. In only one or perhaps two chapters does weather have any bearing on the proceedings.

But to readers of Truman these are peccadilloes, and easily pardoned. The book is awash with interesting information about the cathedral, about Washington and about England (to which the action switches briefly). Most of all, "Murder at the National Cathedral" is an authentic thriller. When readers lay the book aside, they'll be waiting for her next monumental crime novel. Will it be murder at the National Arboretum? At Dumbarton Oaks? At The Washington Post? At RFK Stadium? The reviewer is chairman of the English department at St. Albans School.