The language is noticeably different, and to a modern speaker, English from the 19th century may sound unusually formal and eloquent. Still, English itself hasn't changed so much - we can still read and enjoy these novels without needing a "translation". :)

They are definitely different, but not enough to cause trouble in understanding. 19th-century English is, as Peachey said, more formal-sounding. 如果你的目的你是要能够讲很自然的英语，那这种书可能不太合适。但是，如果你的目的是掌握英文，它们都很好。我最喜欢的这种书是 Pride and Prejudice.