Susan Howatch's latest production number is not so much a sequel to her 1977 best seller, "The Rich Are Different," as it is, simply, a continuation of the antics of that devious little band of selfish neurotics, the Van Zales, and their children and their children's children.

The story line, begun in "Rich" in 1922, picks up in "Sins" in 1949 and takes us right through to 1967, when Cornelius Van Zale appears to get his comeuppance at last for almost 1,300 pages off conspiracy, backstabbing, disloyalty, betrayal, fornication, self-indulgence and lots more. Of course, there's still plenty of time (say, 13 years) for yet another volume, and Cornelius has been in tight spots before, but by this time I, for one, find it hard to be anything but numb about this wheezy old banker and his problem children. Not to mention his stuffy investment bank.

That, for me, is a basic problem with "Sins," as it was getting to be in "Rich." It is very hard to imbue a stuffy investment bank with the kind of drama that hangs about, say, a Cornish tin mine, I'll grant. Rather like pretending as keen an interest in "Wall Street Week" as "Poldark." It may be true of some. Not of me. So that is part of the reason why neither "Rich" nor "Sins" is as satisfying as Howatch's "Penmarric," for example.

"Penmarric" is peopled with characters just as selfish and devious and neurotic and bent on vengeance as the Van Zales and the Sullivans, but those 19th-and early 20th-century upstairs-downstairs tin-coast Cornishmen and women are somehow more alive, more fully dimensional than their cousins-by-author in the Van Zales sagas.

Howatch made you care about her characters in "Penmarric" even when they were at their worst. Parts of the book were imbued with a melancholy that was almost tangible. You could cry for those poor mixed-up anguished souls.

Not quite so in "Rich," and even less so in "Sins."

Dinah Slade might have turned into aSympathetic Major Character, but she disappears after some heroics at Dunkirk at the end of "Rich." Nobody else in all those pages has her class. They're either too dumb, too rotten, too sick or too boring.

There is a considerable amount of indiscriminate sleeping around in this book between cousins, kissing and otherwise, stepsiblings and related friends and spouses, generaly somebody else's. Basically, it is a catalog of musical beds on two continents, with a little international banking hanky-panky thrown in.

Does Scott really love Vicky? or is it just to get back at Vicky's papa, dear old Cornelius, who ruined Scotts's dear old dad back in the first book. (Or does Scott really hate his old dad for running out on Emily, Scott's stepmother?) And what of Vicky and Sebastian? And what of Vicky's kiddies? Stay tuned; I don't think this story ends with this book. And if Darth Vader turned up in the next, it wouldn't surprise me a bit.

This is not to say that Howatch fans (and I am one) will not read every wordabout the next generation of legal and not-so-legal heirs to the parents' sins -- and find it reasonably good beach fare. It is just that these latest cousins are rather less entitled to the emotions one is inclined to invest in best-selling characters.