A number of online reviewers speak to this book being the most readable, engaging introduction to the Myers-Briggs test. It is noted some info might be a little dated such as percentage of population that is I.
Buckingham, Marcus. Keynote speech [on what strengths and how impactful it is knowing and applying] (2009 Video, 9:51) Buckingham is no longer with Gallup but was at this time. This video provides some basics on the strengths concept.