A literary work does not necessarily become depressing or morbid simply because some of its subjects are gloomy, painful, or even grisly. Shakespeare's Macbeth gives us scene after scene of dark atmospheres, crime, natural and supernatural evil, horror, and insanity, yet the play has remained immensely popular for four centuries. Everything depends not on the subject itself but on the writer's treatment of it, meaning technique (manner of presenting the story) and prose style (choices in word, phrase, and sentence).
Heavy, persistent fog is not something that tends to lift spirits and brighten faces. In a story, such a fog may even serve as a symbol of institutional oppression and human confusion and misery. The fog that Dickens creates for Bleak House serves him in exactly that way. And yet it is not, after all, a real-life fog, but a verbal description of the real-life thing. How that depiction is managed — in other words, "expression" — becomes the crucial point, the real issue.
If, by plunging us again and again into the London fog, Dickens is trying to depress us, he is on shaky ground: All of us tend to seek pleasure and avoid pain. If the writing — taken up with an open mind and given a fair trial — really depresses us, we are quite likely to stop reading and declare Dickens an impossible, unreadable author.
