Stylistically, it's very much a throwback to an earlier era, rooted in Fox's high-gloss Scope & Technicolor "women's pictures" of the previous decade, but taking advantage of the greater permissiveness afforded by being made in the late '60s. The tone varies sharply, veering between conventional melodrama to moments bordering on high camp.
Mark Robson's direction is utterly unremarkable throughout, only approaching any kind of distinction in the montage sequences, which eschew the straightforward Classical technique of the rest of the film in favor of some showy double-exposures, slow-motion, and other trippy, psychedelic effects that are very much of their time and ultimately not in keeping with the rest of the film (and were probably largely the work of the visual effects department, in any case). The performances lack any kind of subtlety, and while this admittedly results in some of the film's most unintentionally funny moments, it ultimately has to be chalked up to a failing of Robson's direction.
And yet, despite these issues -- or perhaps because of them -- it's a singularly fascinating film, utterly ridiculous in almost every way, a final gasp from the old studio system, an uneven and problematic film to be sure, but also immensely and undeniably entertaining.