There were no specific book lists about 'Happiness', though there were "self-help"/"motivational"/"life-changing"/etc lists that include such books. Self-help is often looked down on, and is arguably poor and at best a pointless distraction much of the time, but not always. But this list doesn’t have to be just 'self-help', but basically anything that sheds light, whether guidance, whether ideas, maybe even just perspectives, on what happiness really means, how it might be achieved, what and where it isn't, etc, etc. Surely everyone basically would like to be happy, though even that idea is reasonably up for debate, but for sure virtually everyone has a serious interest in the subject, and its key to their lives. Books added here could perhaps be scientifically-grounded studies and/or guides that might at least have practical implications for human life, and/or scientific/philosophical insights into the whole concept and its realities. But maybe even literary works are potentially includable, if they seem very focused on reflection or insight into this issue.