Reading classic novels to improve your writing might be useful, but it does have pitfalls. The bestsellers of yesteryear might have stood the test of time, but that doesn't mean they aren't dated.
    In the mid-19th century, the narrator often broke off from telling the story for a long passage of moralising or description, which probably wouldn't go down well in a contemporary work. They mention public figures who were once famous, and occupations or household items that were commonplace but are unknown now. At least modern readers can usually skip these if they're meaningless to them, but this isn't the case if what is or isn't acceptable behaviour, or the attitudes of the protagonist or narrator are outdated. These can seriously alienate readers. Charlotte Brontë's writing about the capabilities of women has earned her praise for being an early feminist (something she probably wouldn't have recognised). However, her description of the Irish curate, Malone, in Shirley, or her evident approval of Lucy Snowe shutting a pupil in a cupboard in Villette is likely to make modern readers cringe.
    If you want evidence of how styles have changed, compare a historical novel written recently with a novel from the period in which it was set–William Makepeace Thackeray's Vanity Fair with Bernard Cornwell's Sharpe novels, perhaps, or a Jane Austen novel with a contemporary Regency romance. The fact that they are very different doesn't mean that one is better than the other, but trying to write as past masters wrote is unlikely to work today.
    Writers can still benefit from reading classic novels, however. People identify with the characters, and the dilemmas they face draw readers in. The very fact that they show a way of life that's past can be useful, and save today's writers from anachronisms such as having a character drink coffee when it would have been tea, or using a public telephone box without pressing button A.
    In 10 years' time, will your work stand up as well?