I first read this book in a college course about self-deception as a theme in literature. This was by far my favorite of the things we read (we read such other things as Vanity Fair, The Ring and the Book).
This is really a long book about ordinary circumstances in a 19th century rural area in England. So why is a book such as this one considered such a classic even though not many particularly grand events happen?
The book is the study of the ordinary in many ways. You end up seeing how different people live and deal with different situations and what kinds of people they are. At the same time that the reader comes to judgments about the people in the book, George Eliot manages to portray most of her characters sympathetically. Even the worst people in the book are rounded out in some ways and Eliot tries to imbue a sense of humanity. It portrays an "adult" view of the world instead of the simplistic view of the child. In fact, Dorothea makes a journey during the book from a child with a romanticized view to an adult with a more rich understanding through life experience and wisdom.
If you're looking for a book about exciting events, with high drama, with a fast pace, don't bother picking this book up since you'll probably dislike it. This is a book written by a woman and expressing some criticisms of a woman's place in the world of her time. It is also a book that explores a more ordinary setting and viewpoint than perhaps most male authors of the time would write in such depth about. She brings a different experience than most male or female authors of the 19th century. Male authors focused on grander events (their characters often fighting to get somewhere in life) while many female authors showed a romanticized view of life and love. Look at the romances of Jane Austin in which a good marriage seems to be the ultimate goal, or the stormy loves of Emily Bronte in which some strange control/love dynamic becomes magnified to almost heroic proportions. The author is showing something unique, more restrainted, less extreme, more "middle" or ordinary. She manages to pull off a more balanced or "middle" view, also. I noticed some other readers mentioned that it was slow, that they thought events were predictable, or other similar criticisms. These criticisms are valid as far as they go--but they miss the point since these elements aren't really the center of this book.
In fact, Middlemarch is really about a somewhat mundane existance that is inhabited by many people in the real world. We aren't immune to a mundane existance today: work; TV; having enough money to get by; domestic squabbles; eating; relating to other people; perhaps dreaming of something grand but not accomplishing it. There are many events of a mostly ordinary nature that gradually lead one way or another in the lives of people (both ourselves and others around us).
Really this book is about gradual changes, about good acts and bad acts. It's about coming to some state of acceptance and a kind of enlightenment in life. It's about making the unexceptional life one of meaning even when circumstances prevent many large or great things. It's about a hard-to-define quality called "goodness" even absent huge acts or events.
In any case, give this book a read if you like 19th century English literature since it's one of the greats of the period. It's also one of my favorites since I feel as though the author is treating the reader as an adult, without pulling punches, while explaining something about the life that most actual people experience.