This book is basically a mini-wookieepedia and has a LOT of spoilers. I wouldn't recommend this as a first entry into Legends.
It's really more suited for those who read them who want some of Pablo Hildgo's comments about behind-the-scenes details of each... and spoiler, Pablo is very controversial with his opinions. So sometimes you'll get the impression he clearly hated a popular book or character and isn't being fair. Or the subtle, George Lucas doesn't agree with this choice. So it will really sour you experiencing the Expanded Universe/Legends for yourself without others opinions.
As to where to start:
Option 1 (my personal recommendation): for Original trilogy fans/Jedi fans. Start with the Original Thrawn trilogy. It's set 5 years after Endor. Basically, The Rebel Alliance just retook Coruscant and Leia is now pregnant with Twins as Grand Admiral Thrawn prepares the Galactic Empire's counterattack.
Option 2: for Prequel fans/Sith Fans: The Darth Bane trilogy. Set 1,000 years before ep 4, aka 100 years before Yoda's birth. It's basically the Legends retcon that made the Sith go from thousands like the Jedi, to creating the Rule of Two instead.