What is "book of the month"?
One good way to use this site can be to study books together, and post any questions from those books that we may have. The idea is that the text should be one that will stimulate our question-asking faculties, which we then apply by asking questions about the content of book of the month on Buddhism.SE. In the beginning of every month, we start a thread here on meta to suggest and vote for a book. By the 15th, the top voted suggestion is selected. Everyone is free to participate.
I'm opening this thread to get suggestions of buddhism books for reading during this month. One book per answer, please; top voted answer by July 15th can be our book to be studied this month.
There's really no restrictions for book suggestions, other than being available in english. However, books that are freely available are likely to be favored.