The ARRL Amateur Radio Handbook is 1320 pages of technical information on all aspects of amateur radio, in addition to a number of projects and a CD with supplemental information. It and the ARRL Antenna Book are the best amateur radio reference texts in existence. The Handbook has minor revisions each year with the last major rewrite being 2010. I know the digital chapter was updated just this year. This year is their "Centennial Edition" and if you order early you can get a personalized hard cover version with you name and call sign for only $10 more than the soft cover.
Many people bought or inherited older copies. I always hear, "I've been thinking about getting a newer one". I still have my first one from 1993 and just ordered one of these. If you don't have one from 2010 or later, this could be a good opportunity to get a cool current version. Check out http://www.arrl.org/shop/2014-Handbook-Hardcover-Centennial-Edition/.
Snoqualmie Valley Amateur Radio Club