I read this on my Kindle, and my 14 pages of highlights and notes are testament to the fact that I found it highly interesting and helpful in my understanding of how to have a personal relationship with a living God. The bottom line idea that Tozer wishes to portray is that we must use the analogy of any personal relationship we wish to cultivate. "We have almost forgotten that God is a Person and, as such, can be cultivated as any person can." If we want to have a better relationship with a person, we don't go out and read about it (the irony of this statement in a book review does not escape me)...or go to lectures about it...we spend time with that person and try to find out what makes them tick. The entire book is exploring the challenges of doing this with a higher power we can't see.
He does not shirk the challenges of this or the inevitability of doubts, fears, and digressions. This, to me, made the book more authentic. "Whoever will listen will hear the speaking of Heaven...Believing, then, is directing the heart's attention to Jesus."
The only reason I gave it four stars instead of five is because its language--probably by virtue of its having been written in the 1940s--was a bit stilted at times. There were also a few times when I thought he crossed the line into preaching instead of sharing, and also making assumptions about his readers and what they already accept or believe that might not be true.
One of the things I most enjoyed was the prayer at the end of each chapter. In spite of language, these felt very contemporary to me, and resonated with thoughts and feelings that I struggle with in my own prayer life and spiritual journey.
If you have a Kindle, download a sample and see if it seems appealing to you. If you're looking at a hard copy in a bookstore, the Introduction and Preface will give you a good feel for it.