We just finished a very quick read-a-loud which the kids could have easily read on their own called Robinson Crusoe. I knew that it was kind of a classic, but had never read the story for myself. I would say it was alright. There was quite a lot of killing and cannibalism which I'm sure has some level of accuracy for exotic islands, but still a bit more than we are used to. We finished up Swiss Family Robinson (this isn't the exact one, but similiar, I think) a couple months ago which I would recommend much higher-although also a more difficult reading level. Great stories about how the family survived on an uninhabited island and their ingenuity in adapting. In the version we read, there were many words I didn't know so we also added to our vocabulary.
I buy lots of books over the course of a year and most of them I purchase either at yard sales or Goodwill/Salvation Army. It's great to feel free to buy whatever books you want for a quarter rather than multiple dollars for new.