Watching “Diary of a Mad Black Woman” is a truly jarring experience. Rarely has a movie been such a tonal train wreck as this one. The picture, based on a play by Tyler Perry (who’s apparently gained a significant following from his theatrical work), begins as a high-strung soap opera as Helen McCarter (Kimberly Elise), the beautiful wife of Charles (Steve Harris), a rich Atlanta lawyer, is literally thrown out of their plush house by her husband, who’s decided to bring the younger woman (Lisa Marcos) he’s been having an affair with for years–as well as the children they’ve secretly had together–into his home. This part of the film, which ends with Helen arguing with the solicitous moving man (Shemar Moore) enlisted to transport her and her belongings from Charles’ presence, is played like a Ross Hunter movie from the sixties, with lavish locations, beautiful clothes, and fever-pitched melodramatics.

But the atmosphere abruptly changes when Helen takes refuge with her aunt Madea, a huge, boisterous, down-home type played by none other than Perry in ostentatiously unconvincing drag. Her appearance shifts the picture into the realm of pure farce, though of a very labored sort. The makeup is unconvincing to say the least, but it’s the performance that makes your jaw drop–a caricature turn that would have seemed condescending back in the days of Hattie McDaniel. Madea lives in a rambling house along with her brother Joe (Perry again, in old man’s garb this time), an incessantly crude fellow who makes Fred Sanford look like the ultimate in sophistication. (The old woman says at one point that she tolerates Joe living with her because his old-age check helps with the household expenses, but since the house, which serves as a center for neighborhood festivities, looks about as big as the Taj Mahal, that makes little sense.)

Madea’s Lucy-like influence on Helen leads to a frantic sequence in which they go back to the McCarter house and trash it, leading to a “funny” courtroom appearance and the entrance of Joe’s son Brian (Perry again, this time out of Eddie Murphy-esque Klump costume), who just happens to be a lawyer who can get them out of the jam while taking on Helen’s divorce case. Brian adds another tonal piece to a puzzle that already seems wildly out of whack. He’s effectively a single dad because his wife Debrah (Tamara Taylor) is a drug addict who now lives on the streets but pops up occasionally to look wild-eyed and pathetic. Her appearance makes the picture lurch in the direction of gritty drama, but not too far, because simultaneously who should show up but that sensitive moving man, who just happens to be a hard-working friend of Brian’s named Orlando. He falls immediately for Helen and gradually wears down her resistance until they’re at point of engagement. At this point we’re suddenly thrown into sudsy romance mode, with lots of sweet lovin’ and muted hip-hop and jazz simmering in the background.

But of course this movie can’t stay pinned down for long. Charles is the object of a shooting at the hands of a thuggish client that leaves him paralyzed, and Helen, the dutiful still-wife (the divorce not being final) returns to nurse him when his younger lady decamps (with all his money, we’re told, although no financial difficulties appear to result–a good health insurance policy supplemented by AFLAC, one must suppose). But though in her rage Helen first uses the opportunity to brutalize poor Charles, her attitude gradually changes. Because “Diary of a Mad Black Woman,” you see, is also a Christian message picture, with religious tidbits periodically salted into the script (especially by Cicely Tyson as Myrtle, Helen’s nursing-home situated mother); and in the final analysis it’s designed to preach, among all the crass jokes and florid melodramatics, the redemptive power of forgiveness and love. That even goes so far as to take the form of a recovered Debrah returning to the church choir where her young daughter now sings (in a very poor dubbing job) like the next winner of “American Idol.” Brian’s family is thus restored to a contented fullness. But of course that big, hand-clapping reconciliation has to be one-upped by a romantic resolution in which Helen finally leaves Charles after getting him back on his feet and runs feverishly to Orlando, her obvious soul-mate. And the ever-obliging fellow–the perfect man, if ever one existed–sweeps her into her arms for the big finale.

As should be obvious, sitting through this movie is rather like riding a cinematic roller-coaster, and it may well bring on in the viewer the same sort of nausea that those mechanical contraptions in amusement parks often induce. The idea of mixing genres and tones so radically is an intriguing one, but especially as flatly managed by director Darren Grant, it’s not successfully executed. Simply put, there’s no blend here, merely a random potpourri of clashing styles and moods–as in the nearly nutty rehabilitation stuff between Helen and Charles, shrewdly contrived to offer both the feminine revenge fantasy viewers are passionately hoping for and an uplifting postscript implying that vengeance belongs to the Lord alone. Perhaps that’s why Elise looks so bewildered throughout, overdoing things to an even greater extent than in the recent “Woman, Thou Art Loosed.” Harris, whom you may remember from “The Practice,” is more restrained, but his villainous smirks are excessive, and his character transformation at the end is unprepared for. Moore is the very model of studly concern, but Taylor and Marcos both masticate the scenery too broadly, while even Tyson lays on the befuddled shtick rather thick. As for Perry, he proves a multiple threat–and not in a good sense. His Brian suggests that he can give a nice, laid-back performance, but his turns as Madea and Joe are sketch bits that lack the subtlety one would even expect of “Saturday Night Live.” And his script, of course, is rife with problems–not the least of which is Helen’s periodic, cliched narration.

Technically “Diary of a Mad Black Woman” is pretty mediocre, looking rather like a film that desperately wants to match the lushest Hollywood product but always falls short of the mark. There may be a market out there for it, just as there has been for Perry’s plays on the boards. But even its fans will have to admit that the parts never make up an organic whole, and at best the picture is a series of disparate elements that don’t match up. Watching it just might make you a trifle mad, too.