Good, but focused on iPad
This is a copy of the rules from the small rulebook that comes with the Warhammer Island of Blood boxed set (or the rules / reference sections of the big rulebook).
The single biggest reason to own this product is so that you can use an electronic search to find the rule that you are looking for. For example, you can search for the word "building" to find some of the special rules that pertain to buildings but aren't in the Buildings section of the rules. This is the main reason that I bought it, and for the purpose it does the job well.
I mostly interact with the book on my laptop, where the need to click on each special rule or spell is a pain in the butt. However, on the iPad with limited screen real estate it is much better.
Overall, this makes it easier to find rules than the paper version of same, and costs only a little more than purchasing the hard copy of the small rulebook on eBay. If you already have the small rulebook, you are probably better just saving your money.