Go to:
http://www.projectaon.org/, choose you language (in my case english).
Select "Books" from the menu and you will be presented with the list of books broken down by series. You will also see other work listed as well like Combat Heroes and Freeway Warrior.
Choose you book (e.g. Flight from the Dark), and scroll to the contributed section and mobi pocket is there. Most have a low & high resolution version, I personally have chosen all the high-res ones and they work great.
BTW the first book (Flight from the Dark) also has a link to get it direct from Amazon and a link for the hardback version as well.