It is tough to review books like this, written based on video games. Because reading them is far different for someone who just picked it up from a bookstore's shelf than one who sought it adamantly yearning for an extra bit of lore to satiate their ravenous hunger for the video game franchise. I am from the latter. I went on word after word to know more about the world and the lore behind the world of Diablo and Sanctuary, yet, as I was reading it, I kept comparing the narration with The Song of Ice and Fire. It might not be a fair comparison, but I couldn't help myself.
Knaak has tried hard to compel the reader's imagination to run wild by offering mysteries and deceptive clues, just as Martin has done in his books; however, he has failed to keep the readers on toes, for he delivers answers in the next chapter—or in some cases, the next paragraph.
Characters are utterly flat, as is always the case with the stories having biblical tone—their either good or bad—although one character remains an exception: Mendeln. Regardless of my love for the franchise, half the reason I kept reading at a relatively fast pace was this character. Although the ending is not so enigmatic for the main character and plot, it leaves you inquisitive only for Mendeln—a side character.
I would recommend this book only to the Diablo franchise's avid players, not the rest. If you have played the game, I think you must read this book, which is the first entry of a series of novels centred around the game.

Surprisingly not that bad.