Read one, return it, get another. Always have 10 at a time!
Theres something like a $12 million fund and the more KU pages read of my books, the bigger my monthly bonus. Its like icing and another way to make money and I love it. Someone might not want to buy my book or clutter their Kindle with it forever but they want to borrow it and so I make that available.
I also love supporting other writers, knowing they are getting a bonus for me downloading and flipping through or devouring their books. I always try to leave a review before I return the book, unless it was too horrific then I try to not leave one of those 1-star reviews. I might instead track the author down personally and offer some suggestions for improving the book, especially if its nonfiction, since thats the genre I write in.
If you want to check out my current book offerings on Amazon, just follow this link! Its my author page and the one book that only shows paperback is also, of course, available on KU or you can buy it right now for only $2.99 since Im working on the update!