Araby is a superb 93 page Warhammer Fantasy Battle Army pdf by M4cR1II3n (author of the Kislev army book and a Battle Reporter forum member).
The quality of this book is absolutely top notch, even better than the Kislev book !
Araby Army pdf & discussion on Battle Reporter forum
The themed parchment presentation makes it look like a Games Workshop official product (which it isn't). There is a wealth of Araby background (including a history, timeline, map, city descriptions, Araby tribes, and a truly stunning bestiary).
I have not yet delved into the army list in great detail but from what I've seen thus far the rules look to be as good a quality as the presentation.
Thoroughly recommended and well worth your printer ink !