Well, I had to read this one for my Restorations class, and I'm gonna admit, I'm not a big fan. I didn't hate it, but I definitely wasn't pulled into the story. I just didn't enjoy the way that Behn told it. I'm not a fan of books that are overly descriptive, and I like to get to know the narrator. However, Oroonoko is not about the narrator, it's the story of A Royal Slave, Oroonoko, told by the narrator, and I just couldn't get interested in this story the way it was told. It's a novella, but I felt like I was reading this one for a long time. That might be because of the language, but it definitely is not my favourite of the things I've read from the Restoration. If you're planning on picking up something from the Restoration, I'd suggest Alexander Pope or Rochester (John Wilmot the Earl of Rochester) as I found their work much more entertaining. I also really enjoyed the poetry of Anne Finch. :) 
 I will say that I greatly admire Aphra Behn for her work. She was an amazing role model to women of her time, and I think it's great that she did the things that she was so passionate about, especially when society judged her for it. Unfortunately, I just didn't mesh well with her work. Don't let my dislike for her discourage you though, and if you are interested in checking out Oroonoko, you can find it available as an ebook for free online as it's old enough to be past copyright laws. :P