One of the reasons Charles Dickens is still read today, when so many of his contemporaries go unread, is his amazing skill at creating characters. The broken old Doctor Manette is one of his most memorable, and even relatively minor characters like Jerry Cruncher, the English bulldog Miss Pross, and the vile aristocrat Monseigneur the Marquis are brilliantly realized.
Tale is not one of Dickens' best though. He has a tendency to get extremely sentimental and preachy in his novels and Tale is loaded with both. The story relies a little too much on impossible coincidences, but Shakespeare did the same thing. Still, average Dickens is so much better than practically anything else that it seems wrong to fault him for sentimentality and sermonizing.