OK, so you probably just read the word "lengthy" and were all like, "Obviously, Shmoop, this book is long." You could read a page a day and two years later you still wouldn't be finished. That is length if we ever did see it. But we're talking style here, not page numbers. So just take a second to flip through the book – ever notice how some pages never contain even a paragraph break? Some paragraphs just go on and on and on. Not only does George Eliot have a lot to write, but her novel's narrator and characters have a whole lot to say, think, and feel. We see it all.
As for "didactic" – well, that's just a ten-dollar word for something that tries to teach you something. Daniel Deronda is full of literary allusions and quotes that will leave you jumping straight to our "Allusions" section. George Eliot was very well-read, and it seems that she expects her reader to be right up there with her. Never fear, though – you can definitely get through the novel without knowing every single reference, though you might have more fun than you'd expect if you give it a shot.