Reddit mentions of Diablo Archive

The Sin War trilogy is indeed a nice intro, as it details the creation of Sanctuary. After you've read those, I'd recommend reading the Book of Cain and Book of Tyrael, as they formalize the entire lore a little bit. All other books are stories set in the Diablo universe and more or less unrelated to the games, albeit they are great reading. My personal favourites are The Black Road and Moon of the Spider.

TL;DR:

I would read the books in the following order:

The Sin War Trilogy

• Birthright
  
• Scales of the serpent
  
• The veiled prophet
  
  Lore books
  
  
• Book of Cain
  
• Book of Tyrael
  
  Novels
  
  
• Legacy of blood
  
• The black road
  
• Kingdom of shadow
  
• Moon of the spider (this features a char from Kingdom of shadow, so read that first!)
  
• Demonsbane (short story, can be found in this omnibus)
  
  I can't speak for any of the more recent books, as I have not read them yet :)
  
  Enjoy lad!

Before D3 it was fucking epic. Some of the best I have ever encountered in three plus decades of gaming.

After D3 it's still above average and very good, just a lot more cliche and a little less coherent.

FYI, get the giant Diablo Archive book of short stories. It is by far some of the best sword and sorcery I have ever read. Virtually nothing else comes close. Just the first story alone blew my mind the first time I read it and still ranks as one of my all time favorite things to have ever read.

https://www.amazon.com/Diablo-Archive-Richard-Knaak/dp/1416576991/ref=sr_1_10?s=books&ie=UTF8&qid=1527231087&sr=1-10&keywords=diablo