Recently in a sermon, Andrew recommended the book "Knowledge of the Holy" by A.W. Tozer. Since this is a Christian classic, and there are several ways to read it for free, it's worth repeating the recommendation here, and to point you to places you could read it online for free, listen to the audiobook for free, or buy a copy on Amazon. 

Here is an excerpt from Chapter 1: 

"The heaviest obligation lying upon the Christian Church today is to purify and elevate her concept of God until it is once more worthy of Him - and of her. In all her prayers and labors this should have first place. We do the greatest service to the next generation of Christians by passing on to them undimmed and undiminished that noble concept of God which we received from our Hebrew and Christian fathers of generations past. This will prove of greater value to them than anything that art or science can devise."

You can read it as a PDF for free HERE. 

OverDrive is an iPhone app which allows you to check out books (ebooks and audiobooks) from Librarys all over the country for free. You can read them on your device or listen to them on your device. Once you have OverDrive installed, you can get Knowledge of the Holy on OverDrive as a free audiobook HERE.  

Or purchase a paperback HERE on Amazon.