Botany in a Day by Thomas J. Elpel (2004, Paperback)

My whole life I have regretted not taking a botany class in high school or college. A study of this book will more than make up for that deficiency. The book is most useful for identifying the plant families of Montana, and claims nearly comprehensive coverage of the plants found there. The further you get away from Montana the less valuable it is, but even then, many plant families are found worldwide.