C.S. Lewis was my most read author in college, and I am greatly indebted to him for his ability to translate an inherited Christianity into a faith acceptable in the modern world. The Four Loves is a book that fits perfectly into his corpus, but I might not recommend it as the first one to be read. Start with Mere Christianity, and then go from there.
Its not that this book can’t be appreciated on its own. On the contrary, it is very clear in setting forth the differences between the Biblical words used for the English “love”. Its amazing, really, that so many concepts—different in nature—are bound into our very flawed understanding of love today. By reading this book one comes away with the ability to better understand all that is meant by the Bible, and with those eyes, all that is meant by society, which is decidedly less.
For myself, the greatest gain was in understanding that among the loves is the love that involves commitment. Although this lesson was given to me in my youth, Lewis brings it out in a new and fresh way. In fact, in many ways, this is the love that makes all other loves possible, or at least profitable. It is a good read that I highly recommend.

When one thinks of C.S. Lewis's nonfiction, generally the works that come to mind are the apologetics such as Mere Christianity. While there's nothing wrong with that, it's unfortunate that some of his lesser known offerings aren't more fully explored.

Take 'The Four Loves', a beautiful examination of the four 'types' of love we experience- Storge (affection), Eros (sexual passion), Philios (friendship), and Agape (God's love; selfless love). In the hundred and fifty or so pages Lewis leads us through love's trials and tribulations, in the tender, wise prose that is the hallmark of all of his best work. Arguing that we shouldn't avoid love- that in fact, it is the absence of love that makes a Hell, more than any flames or sulfur- he examines how we should best embrace it, and invites readers to examine what place each of the loves plays in his or her own life.

A classic- one many more should read.