Yzabel

I haven't taken the exam yet, so I can't tell whether this is THE book that will help me succeed, or not. However, starting from scratch, I found it made it easy enough to grasp both the concepts and the math—and I was never good at math, so this is quite telling. I'd still supplement it with other materials, though, just to be on the safe side: the exam has changed recently, and some parts (OSPf, for instance) are going to be covered in ICND2, while ICND1 brings back RIP 2. So... Onwards to the 2016 edition, I guess?

N.B. I actually started with Odom's 2004 edition of the Official guide. The 2013 one is much easier to understand when it comes to the math.