Any book Og Mandino ever wrote.  Inspirational and thought-provoking.  My personal favorites: The Choice, The Greatest Salesman In The World, The Greatest Secret In The World, The Greatest Miracle In The World, The Return Of The Ragpicker, A Better Way To Live.

Awaken The Giant Within.  Anthony Robbins, 1991.  How to get your life kick-started to accomplish your dreams.  Motivational.

The Blue Day Book.  Bradley Trevor Grieve, 2000.  A small book that won't take you more than 10 minutes to read.  Keep it handy for a "blue day."  When you're through with the sage advice and the wonderful animal pictures, you'll find that your frown has disappeared.  (You'll have to do a bit of searching in a well-stocked bookstore, or perhaps a greeting card shop, to find this one.)

Eats, Shoots and Leaves.  Lynne Truss, 2003.  This writer and journalist humorously crusades against the sloppy punctuation that is often found in modern writing.  The book is funny, but makes its points well.

The Frugal Gourmet Celebrates Christmas.  Jeff Smith, 1991.  A cookbook with a message.  Smith documents and explains all of the various participants in the classic Christmas manger scene and explains various Christmas and Hanukkah customs around the world.  Interwoven with the cultural tour are various traditional holiday recipes from around the world.  The recipes are top-notch, and the stories are fascinating.  (This book is out of print -- you'll have to look at the various used-book sites in your town and on the Internet to find it.  It's worth the bother.)

The Holy Bible.  My own preference is for the New International version (fortunately for me, available in large print), but the King James version continues to be popular.

How To Win Friends And Influence People.  Dale Carnegie, 1936.  A book that was way ahead of its time.  An updated version is available that has modernized the more dated personal stories, but the advice and techniques are as useful today as they were in the 1930s.

The 7 Habits of Highly Effective People.  Stephen R. Covey, 1989.  A step-by-step approach for solving personal and professional problems with fairness, honesty, integrity and dignity.  Required reading for business types.

Tough Times Never Last, But Tough People Do!  Robert Schuller, 1984.  Inspirational stories of how people (including Dr. Schuller) came through tough times with faith in God.  My copy of this book is well-worn.  I have often loaned this book to friends -- and had trouble getting it back!