Breaking Up Is Hard to Do : UNTIL THE TWELFTH OF NEVER: The Deadly Divorce of Dan & Betty Broderick, <i> By Bella Stumbo (Pocket Books: $22; 546 pp.)</i> : FORSAKING ALL OTHERS: The Real Betty Broderick Story, <i> By Loretta Schwartz-Nobel (Villard Books: $20; 237pp.)</i>

The ugly tale of how La Jolla attorney Dan Broderick dumped his wife Betty for his secretary, and how Betty took revenge on them both, is a human monster movie we can’t seem to tear ourselves away from. Anyone who has ever risked his or her heart for another knows the potential for betrayal, for suffering, for madness and for violence. The 1989 tragedy encompassed every such romantic pitfall, to the unimaginable extreme: Betty Broderick shot her faithless husband and his mistress dead.

Naturally, then, the Broderick case has been laid bare in the daily press and national magazines, dramatized in a two-part made-for-television movie, and now occupies the subject of two recently published books. The far bigger and far better of the two, Bella Stumbo’s “Until the Twelfth of Never,” persuasively depicts the Brodericks as people not so isolated from the mainstream of human conduct. There is something to be learned, Stumbo suggests, from the demise of a woman and a man “who failed almost every step of the way to honor that most ancient, sanest of all social maxims: Do unto others as you would have them do unto you.”

Stumbo, until last spring a longtime Los Angeles Times reporter, has delivered a massive account of the Broderick tale--perhaps over-long, considering that seemingly every one of its 546 pages bears the stain of human behavior at its most dismal. After reading “Until the Twelfth of Never,” even those who lionize Betty will be offended by her, just as those who feel for her murdered ex-husband will regard him as a royal jerk. (Still other readers might find themselves arrested by the notion that the two deserved each other.) It is to the author’s credit that she has not spared us the mutual indecencies, even at the risk of repelling us. Breaking up, after all, is hard to do.

But the Broderick story amounts to more than just a rich parable of a relationship gone disastrously ragged. It also presents a severe, if subtle, challenge to journalists who are themselves human, and themselves predisposed to one side or another when it comes to domestic sagas.

Those who have ever left one partner for another could scarcely resist viewing Betty Broderick as the Ex-Wife From Hell, a wild-eyed woman who would devote the remnants of her life to tormenting her ex-husband with obscene phone messages, driving her car through his front door and threatening repeatedly to blow him away before finally making good on the threat. Likewise, legions of spurned women have hailed Betty as a real-life Thelma and/or Louise--a long-suffering housewife and mother who, as she herself put it, “just decided I didn’t want to be a nice girl anymore. I wanted the life I built, I deserved, I earned. MY LIFE was worth fighting for!”

Such bias has crept into the press, and Stumbo herself has chronicled it. She notes that one women’s magazine chose the headline, “In Hot Blood: Why Did Betty Broderick Wait So Long to Kill Her Husband?” On the other hand, the author dismisses an early story in the Los Angeles Times as a “decidedly unsympathetic” article written by “a young woman about to be married for the first time.”

Yet for all her thorough research and meticulous coverage of the two murder trials, Stumbo’s book suffers greatly, if not fatally, for its own lopsided sympathies. Put bluntly, the author views the murderess as a victim from beginning to end, and sees the deceased as two people who virtually forced Betty Broderick to pull the trigger.

It’s easy to see how Stumbo was seduced by this angle. First, there is only one surviving member of the love triangle, only one principal left to quote; and despite the pathos of Betty Broderick (who is now serving two 15-to-life prison terms), she is masterful at articulating her point of view. As it happens, Betty is surely the most interesting of the three characters anyway. For it is she who sinks to unfathomable depths, and it is she who rears up and avenges her own decline. It’s impossible not to feel for a woman who forfeits 10 years of her young adulthood for the sake of nine pregnancies (five unsuccessful), who lives on the margins of poverty for the sake of her husband’s budding career . . . and is then, at the pinnacle of his success, discarded for a younger, blonder bride. It’s just as hard not to root for this woman who challenges her powerful attorney-husband in divorce court by representing herself, and showing up to trial in four-inch heels so the men in the courtroom can’t look down on her.

Betty Broderick is, in fact, absolutely convincing when she tells Stumbo that the choices came down to suicide or murder--”and that will put an end to it, killing yourself. . . . They would have swept my bones in the back yard and told everyone, ‘See, we told you she was crazy.’ ” One can almost see the mesmerized look in the author’s eyes as Betty adds, “Any normal person would have, a long time ago . . . done something to say I’m not taking this anymore, you sonofabitch. Any man would have beat the living crap out of him six years ago.”

All of this is fine when attempting to understand Betty’s motive for murder. But whatever happened to the promised case study of two people flouting the Golden Rule? Stumbo makes a point of letting us know that, though both parents put themselves above their four children, Dan “set the precedent, by doing it first.” But when Betty throws her eldest daughter out of her house--an act for which the daughter never forgave the mother--Stumbo passes it off as a “strategic mistake.” It’s also mentioned only in passing that Betty attempted to persuade her youngest son to throw boiling water on Linda’s genitals. The author expresses indignation when Dan and Linda file contempt papers on Betty for leaving obscene phone messages, walking into their house uninvited and reading their mail; after all, “she had not at that time committed a single punishable offense.” Stumbo finds Betty’s shortcomings--her inability to argue with a man face-to-face, for example--rooted in her conservative upbringing.

That such an unexceptional past would so severely narrow her human potential is a little hard to buy, but at least Stumbo makes an effort to understand Betty’s limitations. Unfortunately, she doesn’t apply any searching analysis to the behavior of Betty Broderick’s two tormentors. Instead, we see Linda strictly as a compassionless home-wrecker, and Dan as an unyielding automaton. By the end of the story, Betty the murderess/victim is also Betty the self-promoter/press victim, as Stumbo paints her: “Ruined once, Betty Broderick was, in short, ruined twice, this time by her own media appeal. It was never a fair match, Betty’s relationship with the press.” In fact, as the author inadvertently proves, Betty Broderick more than held her own.

In “Forsaking All Others: The Real Betty Broderick Story,” author Loretta Schwartz-Nobel handles the matter of bias by opting out of objectivity altogether. Her slender book has as its aim “a voyage into the soul of a woman,” with Betty as the primary source. Large chunks of the book consist of uninterrupted monologues: “Betty Broderick on Her Early Years With Dan,” “Betty Broderick on the Affair With Linda,” “Betty Broderick on Love,” etc. So entranced does Schwartz-Nobel seem with Betty--or at least with her access to her--that she fails, in her assessment of a woman’s soul, to consider Betty’s elaborate self-deception. Where Stumbo’s book relies on a host of sources to assist in the portrayal of an exceedingly complex woman, Schwartz-Nobel takes the murderer at her word. As a “voyage,” “Forsaking All Others” cannot hope to go the distance.

Then again, there is no danger of anyone interpreting Schwartz-Nobel’s effort as being the last word on this disturbing subject. In contrast, Stumbo’s book reflects both the ambition and the effort of a definitive work, however hampered it may be by prejudices of the heart.