FREE Amazon Kindle books

Does anyone use this great feature. There's some really super books available at the moment. It's ongoing but I haven't used it in ages. Here's one I'm about to download to my laptop as I have Kindle for PC and iPad and Hardcover is usually £20 :) http://www.amazon.co.uk/Seeing-Ourselves-Through-Technology-Wearable-ebook/dp/B00O4CHBKM/ref=sr_1_42?s=books&ie=UTF8&qid=1421197317&sr=1-42