through this link. Note that it automatically adds it to your cart so if you don't get it make sure you remove it.
If you want to look at the product you can goto the normal RPGNow page through this link.
I am not using any type of affiliate ID the one on the first link is for Columbia Games.
There are other discounted PDFs that you can pick and you can see what are the latest by following this thread on the Lythia forum.
The individual articles, like Heru Castle, are often useful as resources for your campaign for when you need it a particular Locale and don't have time to generate one of your own from scratch.