There has been a ridiculous number of movies about psychopathic killers - Silence of the Lambs, Se7en, Copycat, The Cell, etc, etc - and yet for a realistic depiction of a psychopath, this mini-series leaves them all far behind. If you want to see what the average psychopath is like (or perhaps I should say above average, because there is nothing average about Becky Sharp), this is far more true to life than all the others. The reality is that for every Hannibal Lecter in the world, there are a thousand Becky Sharps, and together they do far more damage than all the serial killers. I can only think that Thackeray must have known someone like her, because you can't get this close to reality by sheer imagination, and I don't know of any literary examples he could have copied from.
Of course, the novel, and the series, are about far more than one character - they are in fact about Vanity Fair, the world that Thackerary knew and didn't particularly love, the society which was so warped and hypocritical (rather like ours today, in fact) that it allowed characters like Becky Sharp to prosper.
This is not nearly as pleasant as the usual BBC mini-series, but it is compulsively watchable; the depiction is almost flawless and Natasha Little does a brilliant job portraying the woman we love to hate. The rest of the cast is also excellent, including Nathaniel Parker as Rawdon, the principal victim of his wife's intrigues, Philip Glenister as the lovable but awfully clumsy Dobbin and David Bradley as the appalling baronet Sir Pitt Crawley.