ARC reading is simply this: you get a free copy of the novel. And you provide your honest feedback. Whether that's simply through a Goodreads review, a review on Amazon, a post on Instagram, or other social networks, your feedback is invaluable to authors looking to get their work out. In this way, authors (like me) get more reviews and readers (like you) get to read free copies of great new fantasy books (at least in this case, though any genre can do it).