I hate Knaak. I have all this warcraft novels just for the sake of having them, but never managed to finish a single one. He drags and drags, and reading his books makes me want to kill myself. No.
As for Golden ... I have mixed feelings. I like her stories mind, but I can't help shaking off the feeling that lately she's watering things down to make stuff more "young people" friendly. Azeroth is a cruel, unforgiving world, yet after reading Arthas (which I do love mind - read it 3 times) I feel like I've read some book written for kids and tried to make it seem more adult-player friendly with some fancy words.
I still prefer her miles over Knaak - but perhaps I'm biased and I'd rather read the minutes of the latest Labour party's budget meeting than sitting down for his torture
Arthas I recommend highly if you manage to ignore the silly things - I even have the signed special edition
The Shattering and Twilight of the Aspects ... Thrall, Thrall and more fucking Thrall. I wish they'd stop writing about Thrall.
My favourite warcraft book so far remains The Last Guardian. I was reading that while we were raiding Karazhan, so it had that magical feeling for me.