The 19th century book The King in Yellow by Robert W. Chambers has jumped up the charts on Amazon, and it's no mystery why. The critically acclaimed HBO drama True Detective heavily references the book of short stories. Amazon was selling a Kindle version for $3, which seems like a lot considering the book is in the public domain and can be had for free.

Amazon eventually started offering the book for free too, but there's an important lesson to be learned: If you're looking for a digital version of a book published before 1923, check Project Gutenberg first. The site is filled with titles that have lapsed into the public domain, including Kindle versions of books for download.

Getting these books onto your e-reader is quite easy. Just download the .mobi file and install the Send to Kindle app on your computer. The latter is available for OS X and Windows, and will upload your personal files to Amazon's Whispernet network. Just install and launch the app, and drag the book onto the Send to Kindle window. Before upload, you can even adjust the book's metadata and choose how you want to download the book to your Kindle–via Wi-Fi (free), or with Amazon's Whispernet ($.15MB). Most books are less than a megabyte so if your Kindle is away from a Wi-Fi network and you want to read it right now, the small fee might be worth it.