I just downloaded the free Iphone app. can I purchase add ons like the Hebrew/Aramaic Index to the Septuagint, and other add ons?
The answer is a qualified yes.
To access paid books beyond what you get for signing up for a Logos.com account you need to buy a Logos 4 base package (http://www.logos.com/comparison) or the Minimum Crossgrade ( http://www.logos.com/minimalcrossgrade ).
Not every book in the Logos catalog is available on the iOS app. You can check by looking for the iPhone icon on the product. The Hebrew/Aramaic Index is available see: http://www.logos.com/product/3748/hebrew-aramaic-index-to-the-septuagint
Hi Greg
The real power of Logos is found in the desktop app - which is really really amazing.
You can purchase resources which you can use on the iphone, Mac or Windows PC. The engine is free but the resources cost money.
If you are purchasing for the iphone then make sure that the resource is available for the iphone (it is shown on the product page) not all are.
There is a separate forum for iphone users - there you will get help with anything to do with the iphone app.