Honestly, I mostly just needed the subtitle ("Life in a Minor Key") to reassure me that my struck-with-ennui 7-year-old was within the bounds of normal behavior. Lately my husband and I have been asking ourselves how we suddenly have a mopey 15-year-old in our lives in the body of a young boy, but this book explains it.
I've enjoyed the other age books in this series and try to pick up the coming age just as my children are turning it. Unfortunately, our library didn't have the one for 3 years old, so I'm winging that with his younger brother! ;)
The books, including this one, might not apply exactly to your child. They read a little like a fortune telling in that there's language that "Seven IS like this or that" rather than "could be," but then she also casts a wider net and suggest variations on typical behavior. But I do feel she's basing her descriptions on typical developmental patterns, which apply to many but not necessarily all of children in that age grouping.
One thing I've noticed, and she touches on this in the books as well, is that often there'll be a change halfway through the year. So 2 years old might be compliant and pleasant, but 2.5-3 might be a horror show. It gives me reassurance to read that other parents and kids are going through the same developmental struggles, and hope to know that if things are rotten, they'll change soon enough. (Of course, the other shoe is that things that are going really smoothly will also change, but what are you going to do?)
Many people have expressed distaste with how dated the books are. I'm kind of weird, I guess, in that I find the retro pictures charming. They remind me of my younger brother's childhood. (Yes, I'm now old enough that a book with "old" pictures doesn't even encompass my own childhood. C'est la vie.) I'll admit that the language could use some updating, but I'll take what I can get for now. I don't think being from the 1980s makes these books less valuable.