Somewhere in my digital wanderings, I stumbled across the description of this book as a "serious philosophical inquiry that is a best-seller in Japan." I found instead a somewhat ham-fisted attempt to advocate for Adlerian psychology in the form of a Socratic Dialogue. Which is not necessarily such a bad thing.
There is no subtlety in the formation of this Socratic Dialogue. The two characters speaking are simply named "Youth" and "Philosopher." So, points for directness. As a literary device the problem is that the Youth is naive and feckless, as are most youths, and the Philosopher is condescending and more than a little self-satisfied, as are most philosophers. It's all a bit on-the-nose. I understand the point is the exchange of ideas and not literary quality, but even if something is just pretending to be a work fiction, poor dramatics is distracting.
In any event, it seems the key difference between Adlerian and Freudian psychologies is in determining the cause of one's feelings. A Freudian might say something like, "Your dysfunctional behavior is caused by being abused as a child." An Adlerian might say, "You've chosen to behave dysfunctionally as a reaction to being abused as a child." The plain difference is that Adler says your behavior is your choice, Freud says it is thrust upon you.
In reality these are not as different as they seem. A Freudian would probably treat your dysfunction by invoking your ego (the thing that is not the id or the superego) to rationalize your way to functional behavior. Adler would say you need to find the courage to change your behavior. Either way the prescription is to decide not to be dysfunctional, roughly speaking.
There is a certain appeal to Adler in that he offers you no easy excuse for your behavior. With Adler, you have no opportunity to wallow in victimhood and self-pity. Lord knows that sort of positivism is needed in a world where being a victim, or rather being seen as a victim, is rewarded. Increasingly we are told we are helpless before the elite and privileged. Or perhaps science is explaining how our behavior is just an expression of our genes. Adler makes you responsible for you.
Setting aside how closely it matches reality or not, as an approach to living the one life you have been given, it's probably best to pursue a positive self-empowered course, and not to design lifestyle around dwelling on assuming you're powerless. Such assumptions can be self-fulfilling.
The core concepts that the world has taken from Adler are the fodder of the standard sermons you have heard from our endless self-help sources, from Dale Carnegie to the Serenity Prayer. And there is much wisdom in it, too: self-acceptance and self-value are intertwined with finding meaning in interpersonal relationships. It's good advice if a bit vague. I feel about it the way I feel about Jordan Peterson or any number of philosophers which is that if the bulk of people in the world were to try to live this lifestyle, the world would be measurably improved.
It is not scientific. None of the Austrian founders of psychology -- Freud, Yung, Adler -- were scientific in the sense of being verifiable via experiment. There was also no conception at the time of the dominant psychology model of today which is evo-psych. It would be fascinating to read a reconciliation of Adler and evo-psych. My own bias is that Adler's exhortations work for most everyone in the developed world, where we all run around trying find happiness and meaning. For edge case personalities and folks living hand-to-mouth the detachment from the negative experiences of life is probably not as feasible. I honestly can't say I buy the idea that everyone's unhappiness is due to a lack of courage to change. Maybe most people in most circumstances, but it's hard for me to imagine living an entire life and not having a unhappiness thrust upon you at some point. I have found that large stretches of life can amount to little more than doing crap I don't want to do. I have gotten out of those situations in time, which to Adler, means I found the courage to change. I'm not so sure I didn't just luck out.
Should you read The Courage to be Disliked? Probably not. If you are familiar with the self-help genre (and most people are) you will likely encounter little new information. It is interesting to follow the attempt to translate it into a more formal philosophy, but not especially rewarding. It may anger you because it can seem uncaring and cold-hearted, but that is likely because the vocabulary used for certain concepts, such as "courage" and "inferiority", is primed for misinterpretation. At worst it will be harmless, at best you may gain a nugget of wisdom. But considering the annoying format, you're better off looking elsewhere.