Many scholars argue that a good word to describe this novel is "experimental" because it is only one of two instances when Dickens dwelved in historical fiction aside from Barnaby Rudge. Also, it was only after this novel that Charles Dickens developed the literary techniques required to write a novel of the caliber and complexity of Great Expectations. His literary career hence shows that it seems as if A Tale of Two Cities was the catalyst that helped Dickens develop more accentuated strategies for storytelling.
Also, Dickens's life was going through a series of changes as he was both an actor and a writer. After A Tale of Two Cities, Dickens solidifies himself as a writer exclusively and dedicates himself to theme development and richer character creation.
This is the only book by Charles Dickens (well, besides A Christmas Carol) that I love. A Tale of Two Cities is an historical, romantic novel set during the time of the French Revolution. Sydney Carton, a very crass and hateful man, falls in love with the beautiful Lucie. Sadly, however, Lucie is in love with another man, Charles Darnay. Unfortunately, Charles is accused of going against the Revolution and is condemned to death. Sydney Carton's love of Lucie is so strong that he decides to take Darnay's place and die at the guillotine so that Lucie can spend a lifetime by her love's side. Right before his death, Carton says, ""It is a far, far better thing that I do, than I have ever done; it is a far, far better rest that I go to than I have ever known." He dies knowing he sacrficed himself for the one he loves, and had therefore redeemed himself as a human being. So, in one word, I would describe the novel as "romantic".