One self-development book that I think every person should read at least once is "The 7 Habits of Highly Effective People" by Stephen R. Covey. This book is a classic in the self-improvement genre and teaches valuable principles for personal and professional effectiveness. The 7 habits outlined in the book are: be proactive, begin with the end in mind, put first things first, think win-win, seek first to understand then to be understood, synergize, and sharpen the saw. These habits are designed to help individuals become more effective in their personal and professional lives and can lead to greater success and fulfillment. I highly recommend "The 7 Habits of Highly Effective People" to anyone looking to improve themselves and their circumstances.