As I wrote earlier, the book is a practice for watching your mind throughout the day. and what happens as a result is remarkable.
The process is simple. six times throughout the day you stop and see how you've been treating others. as is demonstrated to the left, first you write a '+' (one good thing you've done recently). Next you write down a '-' (something harmful you've done). And finally for each entry you write a 'todo'. The todo is one real action you are going to do to counteract the negative thing you just wrote about.
It's simple.
To make things even more interesting and to get better results each of the six-daily entries can be associated with a specific act. For example, the first entry of the day could be generosity. In that case you would enter a '+', '-', and 'todo' regarding how giving you've been in the past 24 hours. The second entry of the day could be regarding speaking kindly, and so on.
If you have some spiritual tradition, use a list from that belief system. The Judeo-Christian ten commandments, the Buddhist ten virtues, or the five pillars of Islam are perfect for keeping a book. Simply rotate through the lists so that each of the six book entries is pertaining to a different commandment, virtue, or pillar.
There is a wonderful pdf of how to do the book from a Buddhist perspective. The teaching by Geshe Michael Roach goes into great detail about the book practice. I highly recommend it for anyone who wants to live a good life.