If you've ever read Francis Chan before (Crazy Love: Overwhelmed by a Relentless God
) then you'll know that he's incredibly easy to get on with. His style is more inquisitive than lecturing. By laying out simple principles Chan then places the onus squarely on the reader, "What are you going to do about it?"
If you're expecting a strong doctrinal treatment of the Holy Spirit then you'll probably be disappointed. But if you want a book that will make you think, question, get down on your knees and pray about what your reading then this is it.
Chan's emphasis is to encourage the reader to live a life dependant on God the Holy Spirit, a life seeking to know God more intimately and serve others rather than yourself.
The book also has a strong emphasis on the fruit of the Spirit. Rather than placing a premium on showing the gifts of the Spirit (which should be used for the Churches benefit not our own) a Spirit filled Christian will be demonstrating a supernatural level of the fruit according to Chan.
He leaves us with the ultimate test, how much different would our lives be if we didn't have the Spirit?
I'd recommend The Forgotten God to anyone whose after a light read but also to anyone who wants to be challenged in their view of the Holy Spirit.