Depends on exactly what you're looking for with Dickens. If you are looking for comedy, sentimentality, and characterization, you may want to start at the beginning with PICKWICK PAPERS, or perhaps THE OLD CURIOSITY SHOP.
I, though, might go with DAVID COPPERFIELD. It is a fantastic novel, Dickens' professed favorite, and gives you a good idea of the scope of Dickens--both in terms of social issues, great characterization characterization, and intricacies of plot and coincidence--all of which work their way through his work. It also sits at the center of his oeuvre, bestriding the "early" comical Dickens and the "late" serious.
If you just want a shorter look at something characteristically Dickens, rather than the 1000 pages of COPPERFIELD, I would probably go with GREAT EXPECTATIONS (short...500 pages ;) ). This is a great work and, while it is a staple of high schools, it is well written and deep.
A popular book, but one I would avoid if your looking for a taste of Dickens is A TALE OF TWO CITIES. It is good, it is just not quite Dickensian.
If you start with COPPERFIELD, you'll get an idea of the size and scope of Dickens, and then you'll be ready for his mature great works such as BLEAK HOUSE, LITTLE DORRIT, and OUR MUTUAL FRIEND.
I think I am going to start with Great Expectations. Will read over Christmas break when I will have more time to devote to reading.. I did buy Bleakhouse but thought that it did not look like a good one to start with.
Drew got it about exactly right. I would only urge a little more strongly that you start with Pickwick. It reveals an explosion of creativity from a budding genius, and the sense of excitement Dickens obviously felt at the discovery of his gift is tangible. As time went on the world weighed more heavily on him, and while all his novels are worthwhile, the are never again as much fun for him or us.
I agree w/ the other posters; David Copperfield, or Pickwick Papers etc....his books are all long, that is because he wrote serial magazine stories, so the readers had to wait breathlessly for the next installment, if you notice many chapters end w/ a sort of cliffhanger...Dickens was so hugely popular that people were lined by the hundreds on the docks of New York waiting for the ships from Britain to bring the latest installments.
If you become interested in Dickens, or for anyone reading this who is interested, the best bio of him, by far, is by the Englishman Peter Ackroyd. There are two versions of his book--same title and photo on cover, try to get the one that is a little over 200 pages vs the much shorter one. "Dickens: Public Life and Private Passion (Paperback) by Peter Ackroyd".
Ackroyd really explains Dickens: his awful childhood, his striving to be a success, the demons that haunted him all his life, from his childhood, supposedly he'd walk for hours at night through all parts of London (NOT a safe place then) because he couldn't sleep.
HEre is Amazon's editorial review of that book: Editorial Reviews From Publishers Weekly Ackroyd ( The Last Testament of Oscar Wilde ) is a master biographer with a seductive prose style, and this massive volume is likely to stand as the Dickens biography for decades to come. Ackroyd moves around with authority in the world of the ebullient, ambitious, insecure, haunted, theatrical genius, which is also the world of early and mid-Victorian England assimilated and transformed to a stupefying degree. We read about Dickens's penurious and painful childhood; the triumphant reception of his first novel, The Pickwick Papers ; the prodigious flow of subsequent novels which, though increasingly somber in tone, continued to reflect a mind whose primary reaction to experience was anarchic laughter; the two trips to America, for the most part wildly successful; the scandal surrounding Dickens's desertion of his wife. And Ackroyd pinpoints Dickens's two great innovations: he was the first to introduce the language of the romantic poets into the novel; and his dramatic public readings from his novels constituted a new art form. Illustrations.