This depends on many different factors.  How quickly do you read?  How is your reading comprehension?  How much free time do you have each day to dedicate to reading?  How well do you like the story?

Jane Austen's books tend to be filled with very long exchanges of dialogue, character analysis, and descriptions, so the going is a bit more slow than an action-packed adventure novel.  It tends to be quite thick and plodding, and requires a lot of concentration.  The bottom line is that you won't be able to get it read in a few hours; more like days, and even longer depending on how much time you read each day.  It's a great story though, and well worth the time.  I have provided some links below that might help you to understand the plot and characters a bit better, which might help you pick up the pace.  Good luck!