I have long been interested in personality. I read an informal book called Please Understand Me when I was a young boy, which was a popular book on the subject of personality. When I became an adult, I found and read its sequel, and enjoyed that as well.
These treatments of personality are not as scientifically valid as some others, as people often test as a different type when they retake the tests. Nonetheless, in their informal way, these have been among the more valuable books I've read for understanding others.
It is fitting to mention here that I don't believe that any personality is better than any other. Some types might be better than others at certain types of things, but their value as human beings is not affected by their personalities.
Dieter F. Uchtdorf
In the words of President Dieter F. Uchtdorf: "While the Atonement is meant to help us all become more like Christ, it is not meant to make us all the same. Sometimes we confuse differences in personality with sin. We can even make the mistake of thinking that because someone is different from us, it must mean they are not pleasing to God. This line of thinking leads some to believe that the Church wants to create every member from a single mold - that each one should look, feel, think, and behave like every other. This would contradict the genius of God, who created every man different from his brother, every son different from his father. Even identical twins are not identical in their personalities and spiritual identities.
"It also contradicts the intent and purposes of the Church of Jesus Christ, which acknowledges and protects the moral agency - with all its far-reaching consequences - of each and every one of God's children. As disciples of Jesus Christ, we are united in our testimony of the restored gospel and our commitment to keep God's commandments. But we are diverse in our cultural, social, and political preferences.
"The Church thrives when we take advantage of this diversity and encourage each other to develop and use our talents to lift and strengthen our fellow disciples." (Source: April 2013 General Conference talk)
I have found it helpful to know my own personality type (I am an INTJ), but it has also been helpful to understand the types of others. For those in my family, I have links here to each of your personality types, if you ever want to read about them. Most people don't completely match everything in their type description, but usually one type description fits better than the others.
Here are the links:
My sister Katie
Her husband Tim
My brother Eric
If you're curious about what type you are, the test can be taken at this link. (Please note that I am not trying to convince anyone to take this test - only to provide those that want to with the means of doing so.)
So that's what I've learned from this study of personality. I hope this has been helpful to someone.
My other post about psychology