Think and Grow Rich by Napoleon Hill is a classic book in the personal development genre.
I have recently read it (twice in a row) and gained so many interesting techniques and little nuggets of wisdom.
One thing that I found very interesting was the Personal Inventory Self Analysis Questions (download pdf here). It was a series of questions that yielded some very revealing insights.
Also, during my period of self-reflection between Christmas and New Year’s Eve when I set my personal 5 Oaths for the year, I will now use the Self-Analysis Questionnaire for Personal Inventory (click for pdf download) from the book.