While the book covers races and factions that aren't playable in WoW (with the exception of the Pandaren), the table of contents contains a slew of names that are familiar to even a lapsed WoW player such as myself. I briefly considered running a WoW tabletop game for my kids, when they were all into the MMO, but ended up sticking with our D&D campaign in the Nentir Vale, at the time. However, this book made it tempting to run a story that wasn't focused on the Alliance-Horde conflict, as it details so many factions (not all of which are "dark"). I never did more than skim the book, but I would imagine it would come in quite handy to further flesh out Azeroth, or to fill in some backstory for the MMO players who enjoy the lore.
Here are the first couple paragraphs from the introduction, which I found helpful to remind me what's in the book.
World of Warcraft: Dark Factions wrote:You might subtitle this book the Independent Player’s Guide, since it does for many independent, dark and neutral factions what the Alliance and Horde Player’s Guides do for the Alliance and Horde. This book details many races that are important in the Warcraft world but are not members of the Alliance or Horde. It also details many factions. . .that have their own motivations,intrigues and agendas. They all possess a degree of separation from the Alliance or Horde, though they are of concern to Alliance and Horde characters.
Specifically, this book is concerned with the following races and factions.
Races: Dark Iron dwarves, dragonspawn, murlocs, naga, pandaren, quilboar, satyrs and tuskarr.
Factions: The Argent Dawn, the Atal’ai and Hakkari, the Cenarion Circle, the Cult of the Damned, the Dark Horde, the Darkmoon Faire, the Defias Brotherhood, the dragonflights (all fi ve), the Earthen Ring, the Explorers’ League, the Farstriders, the Scarlet Crusade, the Syndicate, the Thorium Brotherhood, the Twilight’s Hammer, the Zandalar troll tribe.