This book is well worth the read because Piper manages to write in an engaging manner, while at the same time dealing with deep theological issues. One of the best sections of Finally Alive focuses on God's action in the regeneration process. Piper explains how God regenerates the human heart, making it possible for humans (who had been dead in sin) to respond to the gospel in repentance and faith.
Some readers of this book will not like it because Piper emphasizes God's sovereign action in the process of the new birth. The problem for those readers is that Piper supports what he says with scripture. Spending much time in I Peter and I John, Piper also talks about the new birth bringing about evidence in a saved person's life.