C. S. Lewis' Letters to Malcolm is a collection of letters written to an imaginary (I think) friend, Malcolm. The book was published in 1964 and was the last Lewis wrote before his death in 1963. It contains 22 letters dealing with a variety of topics including prayer, liturgy, God's omniscience, "religion," liberal Christianity, metaphysics, and heaven.
Having only limited exposure to Lewis' work, namely parts of Mere Christianity, The Screwtape Letters, and The Chronicles of Narnia, it is hard to compare Letters to Malcolm with his other writings. So, I think I'll steer clear of that. The book itself is an interesting read. The subtitle is a bit misleading, as each letter deals with one or more theological topics---at times it is hard to figure out how some of the topics relate to prayer at all. Lewis' intellect (he was brilliant) shines throughout the letters and provides readers with a provocative glimpse into his theology. The letters/chapters dealing specifically with prayer and heaven were by far my favorites.
My experience in reading the book was somewhat like walking and falling into a pit and then getting back out again. I found myself fascinated by, and reading carefully through the first five letters, hurriedly fighting my way through the middle section of the book, and then fascinated by the last four letters. I think part of it was due to my tendency to be far too practically minded, and the rest due to the fact that I know very little of philosophy and metaphysics, not to mention Latin.
As far as a recommendation goes, I like the book, but I don't think Letters to Malcolm is a very good starting place for someone interested in Lewis. It is also not a book for someone looking for practical advice on prayer.
Here are three of my favorite quotes:
...I am often, I believe, praying for others when I should be doing things for them (66).
I have met no people who fully disbelieved in Hell and also had a life-giving belief in Heaven (76).
The truth is, I haven't any language weak enough to depict the weakness of my spiritual life (113).