The Legend of Zelda: Hyrule Historia is a massive encyclopedia stuffed full of rare Zelda facts. The tome, originally released in 2013, binds 276 pages in a heavy hardcover. It's a big, beefy boy, which is why it's a relief to hear a digital edition is on the way next month.
If you spin-slash your way over to Amazon, you can see the pre-order page for the digital edition of Hyrule Historia yourself. It's compatible with Kindle and the ComiXology app, and it's available on April 14. While it usually retails for $22.35 USD, it's currently on sale for $12.07 USD.
Hyrule Historia isn't just packed with rare art and translated production notes. It also contains the infamous Zelda timeline, a quagmire of multiple timelines and parallel worlds. While it's fun to sit down with a cup of tea and read about how destiny did doughnuts all over Hyrule's lawn, you shouldn't take the timeline very seriously. Even Zelda series producer Eiji Aonuma says so.
Do, however, pay close attention to the included manga by writer Akira Himekawa, who's produced other Zelda manga in the past. It gives insight into how Link became the chosen hero in The Legend of Zelda: Skyward Sword, and how he acquired his unique red Loftwing mount.
Dark Horse published several companion tomes for Hyrule Historia, including The Legend of Zelda Encyclopedia and The Legend of Zelda: Art and Artifacts. These newer books are already available in digital format, so you can save yourself some back strain.