A lot of books about houseplants seem to usually be organized by the plants' scientific classification, which is kind of esoteric and not particularly important to most people who just happen to like plants in their home. This book hits on a much more useful scheme: organizing plants around how much light they are likely to get. That's what the "five exposures" (i.e. light exposures) are. Those of you out there with green thumbs may be reading this and saying "Well, duh.. didn't you know before how much light your plants should be getting?" and unfortunatley, the answer is "no". I like having plants around, but I am a complete dilitante when it comes to taking care of them. This book is obviously aimed at people like me, and it is a welcome step in the right direction!