If one wants to know the how, when, where, and why of Jewish observance, I can't imaging a better source of answers than THE BOOK OF OUR HERITAGE. For ease of use the book is broken down by month and then, chronologically, by days of importance.
In addition to presenting biblical and historical reasons for just about everything, it even explains differences in tradition and methods of observance between various Jewish sects.
I don't read Hebrew, except at the most elemental level, so I can't speak for the original, but the translation is written in such a clear manner that even the most complex issues are made comprehensible. For someone like me, who is only vaguely aware of many of the less well-known traditions and requirements, this book is a gold mine of information.
THE BOOK OF OUR HERITAGE covers all phases of the calendar year, holidays, fast days, days of joy, and days of sorrow. It clarifies both the meaning of the law and the appropriate methods of observance. It gives Rabbinical interpretations and insights of the Sages throughout Jewish history. Until reading the comments contained herein, I never really understood why, as a child, I asked the "Four Questions" at the Passover Seder, and I certainly never understood the deeper significance of the answers I received. Now I do.
This is a reference that should be on the bookshelf in every Jewish home.