Austen is the most accessible of all of these authors and her novels are relatively short. Dickens isn't really that bad, but he has some quite long descriptive paragraphs with some possibly difficult words, and his dialogue often includes somewhat odd dialect or archaic expressions represented in a nonstandard phonetic way. Shakespeare has the most archaic, but beautiful, language. If you find it difficult, I would recommend Tales from Shakespeare by Charles Lamb and Mary Lamb (available online here: http://www.gutenberg.org/ebooks/1286), which was written to make the stories accessible to children who might have had the same issues. It is also a C19th text, but given its original audience, still very accessible today.

What exactly are you finding difficult? For Shakespeare, it helps to read it aloud - he added a lot of clever word-play into his texts, and simply reading it robs you of half the fun.