The Happiness Project (although I felt tired after reading it), had some reservations about Happier at Home, but I really liked Better Than Before. I think it has a lot to do with the fact that I like Gretchen Rubin way more ever since I started listening to her podcast, Happier. (Thanks to Amy for recommending the podcast to me!)
On the podcast, Gretchen and her sister, Elizabeth, come across as very friendly, down-to-earth ladies, and I love listening to them each week. So I really liked Better Than Before. It's all about habits, how you work as a person, and how creating better habits can make our lives happier.
Highly recommended to anyone interested in being more aware about how you work, and how to add better habits to your life.
PS: This is the book I read for the category "a book published this year" in the Modern Mrs. Darcy 2015 Reading Challenge.