I listened to the audiobook version of this; there was a person credited for reading it so I assume it wasn't a robot, but it really sounded like one. This surprised me a little since I think it's well-known that people don't really find voices like that to be "likable" and you'd think someone with a pleasant, personable voice would have read this book, but whatever. At least the book is short and to the point.
I saw someone in another review criticize the author for simply gathering the advice of others and not having many original ideas in this book, but to me, that seems like a silly criticism, given that the subtitle of the book basically says outright that the content of this book is an overview of scientific studies about "likability". The whole point of the book is that the author gathered existing research together. He has his own ideas in his other books (I assume, I haven't read them). He does include commentary on the results of each study and how a person might try to apply the information to their own social interactions, which I think is really exactly what I expected of the book.
So 4 stars for being EXACTLY WHAT I EXPECTED (and exactly what it says in the title).
In terms of the content itself: I myself didn't learn a ton but I didn't really expect to, since this is not the first time I've looked into this topic. I just think it's interesting, because when I was young, I didn't have great social skills and I assumed that social skills were a thing you either had "naturally" or did not have. When I was in my early 20s, I got advice from a good friend which forced me to realize that in fact, social skills can be learned (and improved with practice) like any other skill, and while we each have different starting points and learning capabilities, anyone can improve their existing skill, and there's no excuse for not improving other than a lack of will.
After that, I actually made an effort. I learned a lot of the things in this book subconsciously, after various difficult times in my life forced me to actually need and rely upon social skills (not to make friends, but to interact positively with people who could help me, as well as coworkers, etc). I enjoyed hearing these concepts laid out clearly in words even though I wasn't surprised by them.
Reading a book might feel like a very cold and calculating method of learning social skills to some people, but if I had read it as a teenager or in my early 20s, when I still thought of socializing with "normal" people as a kind of boring and impenetrable enigma, I think it might have been very illuminating in some ways. Many people are awkward with others, so they avoid social interaction whenever possible (which is often easy in our technologically connected world). Without practice, it's difficult to learn these concepts on your own, certainly not at the age where it would be most useful (when you're young). I think the kind of person that this information would be most useful to is also the sort of person who'd be interested in reading a book like this.