The British made a long, long film adaptation of Little Dorrit which is a masterpiece. It comes in two parts, each almost three hours long. The first is called "Nobody's Fault" and the second is called "Little Dorrit." They should be seen in that order. If you watch this film you will almost certainly want to read the book. Unfortunately, it is only available on two videotapes and not on DVD. It stars Alec Guiness and Derek Jacobi. I believe that a more recent film version was made which I haven't seen. I believe there was some sort of agreement that the original version wouoldn't be released on DVD for some time in order to avoid competing with the new version--or something like that. But it is the old 1988 version I am recommending. It made Little Dorrit my favorite Dickens novel. It deals with the Marshalsea debtors prison. What a place!

If I had some time to devote to reading some Dickens right now, I might want to have a look at American Notes. It would be fascinating to see what Dickens thought about the United States during an immensely important period in the development of our nation. It would also be very interesting to read some nonfiction by one of the world's great writers of fiction.

I, too would recommend A Christmas Carol. You have probably seen a stage or screen adaptation of the novel, but that is why reading the actual text might be even more interesting. What elements of the novel's language have transcended these scripts? How are the ghosts described? How much do you learn about Scrooge's motivations and background to provide a better understanding of why he acts the way he does? There is a lot of be learned from the reading the novel.

I would also have to suggest A Christmas Carol. Given its "comeback" after Jim Carrey's portrayal of Scrooge, many students and adults are picking up the novel. The characters and action of the novel is elegant and curious at the same time.

There are still several others worth reading. I'd start with The Old Curiosity Shop--the best of the ones you haven't read--and then go with Little Dorrit and Edwin Drood.

I see you don't have A Christmas Carol on your list, which is a quick easy read, and familiar story.  Other than that, you might be interested in some of his short stories.  I am always intrigued when authors can master the art of the novel as well as short stories.