Here are some of my thoughts re: the introduction.
St. Theophan begins the third paragraph with a description of me, and for that matter, I suspect, most of us (at least at some point or the other). "For the most part, the very desire to walk is lacking. The soul, attracted by some passion or other, stubbornly repulses every compelling force and every call; the eyes turn away from God and do not want to look at Him. The law of Christ is not to one's liking; there is no disposition even to listen to it." (p.21) It's easy enough for us on this site to say that we are and be willing in the spirit to walk along the Way, but the flesh is weak, and his description, while only a few lines, is dead on. If we are really honest with ourselves, we don't even want to hear any of it, let alone actually do it.
At the bottom of p. 22 going onto the top of p. 23 (and these page references are to the paperback, which is what I'm assuming everyone is using), he discusses how a Christian becomes such after birth, rather than becoming one by birth. Nicodemus rightly points out that this is the way other religions and cultures view religion, but it is not the Christian way. Nevertheless, even we fall into this mentality: "cradle Catholics", "cradle Orthodox", and all that. But what really struck me about this section was the relevance of a passage from Galatians. St. Theophan writes that the naturally born man is injured, fallen, and opposed to Christianity, and then writes that while a plant begins life with the awakening of a dormant power within, the beginning of Christian life is "a kind of recreation, an endowing of new powers, of new life." The power is from without, and this is where St. Paul comes in:
For I through the law am dead to the law, that I might live unto God. I am crucified with Christ: neverthless I live; yet not I, but Christ liveth in me: and the life which I now live in the flesh I live by the faith of the Son of God, who loved me, and gave himself for me. (Galatians 2.19-20, RSV)
He is the Power from without, and if we are in Him, we are "a new creature: old things are passed away; behold, all things are become new." (II Cor. 5.17)
Finally, a question: in the middle of the same page, St. Theophan writes that Christian growth entails a lot of struggle against oneself, and that it goes against our natural inclinations. A non-believer would probably wonder what the point of fighting one's own nature would be, since it comes naturally and is not something freely chosen; will St. Theophan answer this in the book, or would one have to find the answer to that elsewhere?