OK, so I'm reading it a little early since I'm not quite 50 yet. But Amazon had one of those deals where you get a discount if you buy 2 related titles, and it turned out to be a pleasant surprise. The author's emphasis is not on having a ton of clothes but on having exactly the clothes needed and to be in style without sacrificing comfort and fit.
One of the keys to her wardrobing strategy is to list your usual activities during a typical 14 day period. All of them, even if you do them only occasionally. Don't worry if it's not perfect, it's supposed to provide a general guide to the type of activities you do. Come up with as many 14 day plans as you need--for example, if you're a teacher with summers off, you'd have a plan for the school year and a plan for the summer. Or if you live in the North but spend winters in Florida or Arizona, you'd need an acitivity list for each. You get the idea.
After doing this exercise, you can see what your lifestyle needs are and develop your wardrobe from there. The author does have an opinion about what sort of items should be in a wardrobe (they all do), but I like that she comes from the standpoint of "what do you need?" vs. "you should always wear these."
Related was the concept of "private dress code", the clothes you wear when relaxing or hanging out, and "public uniform," outfits that fit the general public's expectation of what's suitable or appropriate for a particular situation. Your wardrobe should have both, but the proportion of each is based on those 14 day activity lists. In my life, I have a lot of "public uniforms" because I work in sales and I'm representing my employer. If I were retired or a SAHM, I'd have more clothes that fit my "private dress code." However you always need a few "public" things--it's awful to have to throw a decent outfit together if you get a last minute invitation to an event or have to go to a funeral. She also considers what clothes to have that can dress up or down.
And yes, there is discussion of black. She likes it, also charcoal gray and brown. Readers, I know that some of you are opposed to black or navy or brown or gray--whatever--we all have basic colors we hate. But having basic, even bland colors in your wardrobe is helpful. They provide a base you can work from--the more fun colors are your accents that create your look. Think about it, how often can you really wear a fun colored suit? Once a month? Twice? But a basic colored suit could be worn many times in a month without getting "the eye" from your co-workers, as long as you vary the top you wear with it and the accessories. You could even break it up and wear the pieces separately.
This book is relatively small, with short chapters and large print. Not a lot of "filler" to bulk it up. It doesn't have a lot of photos like What Not to Wear and similar books, but it does have a lot of ideas. It seems like the author truly lives what she writes about, and I appreciate that.