Lewis reflects on the nature of four different meanings of love, found in four different Greek words: Storge, Phileo, Eros, and Agape. The first, which he calls "affection," refers to dutiful, loyal, familial love. It is care that arises from sentiment and pity. The second, which he calls "friendship," is based on commonality, appreciation, and choice. The third, simply referred to as "eros," refers to the romantic, possessive desires. Finally, Agape, or "charity," refers to the heavenly, unconditional, sacrificial love that needs nothing in return.

As with other non-fiction works of his, Lewis draws applications from is contemporary society that may stretch the reader's mind, in trying to relate. Yet, if one can get into the mindset of the author, his insights are quite helpful and applicable today.