I feel like the definition of "Single at Heart" is still too ill defined for me to truly grasp the concept. The idea seems to be both too inclusive by stating that anyone can identify as single as heart, even those in active romantic relationships, but yet it's too exclusionary by regularly stating specific characteristics that define someone that is single at heart and not matching those characteristics indicate that the subject is simply just unafraid of being single or actually aspires for a romantic relationship. It also very barely touches on asexuality and aromantic, keeping the concepts contained to only chapter 7, which is surprising given how these sexualities can likely be incredibly intertwined with this concept of "single at heart" if the author chose to do deeper research on them. 

The true benefit to this book is that it serves as a direct challenge to compulsory coupling and the idea that being in a relationship gives you an automatic advantage in life. It's a great exploration of the advantages of remaining single and prioritizing solitude over the expected partnership demanded in our society to prove that you're a "real" adult. I especially enjoyed the chapter studying the difference in happiness levels between single adults and married adults and how single adults are regularly happier than married folks, but society perceives them as less so due to their lack of relationship status. 

Also the writing style is a bit woo-woo and quote heavy for my tastes, but at least it made it a quicker than expected read.