I originally read about Marie Kondo and her book in the New York Times and thought that it might be interesting, but that I didn't have any particular need for it. After all, I live in a fairly small apartment in NYC, and there simply is not much room to accumulate clutter. I was also already accustomed to going through my closet every three months or so to cull unwanted items that I could donate or discard. However, an alum of my college recently mentioned how the book had helped her to think about her stuff and her clothing in a more minimalist way, which made me want to read it for myself.
Marie Kondo's The Life-Changing Magic of Tidying Up is primarily about the act of "tidying up" or decluttering one's home in one fell swoop, mostly by discarding things that are no longer useful. However, I agree with the alum that described it as ultimately being a book about minimalism as a broader concept. Her primary overall point is that first and foremost, one should discard items that no longer or never inspired joy. The process of going through one's belongings and making decisions about whether an item is worth keeping under that criteria is then helpful for better understanding the type of life one wants to live and what is important in one's life.
A few choice quotes:
Through the process of selecting only those things that inspire joy, you can identify precisely what you love and what you need. - p. 126
... one of the magical effects of tidying is confidence in your decision-making capacity. Tidying means taking each item in your hand, asking yourself whether it sparks joy, and deciding on this basis whether or not to keep it. By repeating this process hundreds and thousands of times, we naturally hone our decision-making skills. - p. 178
The question of what you want to own is actually the question of how you want to live your life. - p. 182
In short, I quite enjoyed the book. It is a quick read and Kondo's general suggestions are based on using intuition rather than setting out unnecessarily detailed or specific suggestions or rules that might not work for everyone.