Madonna has written a children's book, called The English Roses. Yesterday's Times T2 Magazine had some quite complimentary reactions from various celebrity mums. (There is now a link for this, but links to timesonline are often a problem after a few days for non-UK people, so just take my word for this.) Their children liked the book very much, even though (because?) a lot of them have now never heard of Madonna.
From the sound of the various reactions, the story is a re-hash of the poor little rich girl story, only this time it's a poor little beautiful girl. Beauty is now wealth, I guess. And the moral is, don't be nasty to poor little beautiful girls.
Written from the heart, I think we can say. (Don't write mean reviews saying that some poor little beautiful girl is utter garbage in her latest movie, just because she is utter garbage …?)
But isn't that what good art does, whether "popular" or high. It takes real experience and rejigs it and universalises it. The idea that you can just slosh out "popular" art with one hand, emotionally speaking tied behind your back, is very, very wrong. You have to mean it.
This could obviously be a culture posting, but I have the feeling that all culture vultures who care already know about this Madonna book, while there may be educationalistical readers (all complaints about academic standards but no interest in the Zeitgeist) who missed this event completely. And a children's book that children like a lot is an educational as well as a cultural event.
I suspect that many creative people, whether celebs or not, contemplate a dash at children's fiction at some point. The great majority of it is so obviously just sloshed out, as you put it, it's very tempting to say to oneself, "You know, I could do so much better."
Talent in writing, though, is not given to all - and still less so the ability to tell a story well. A neighbour of mine, a screenwriter of many years standing and nearly a Bafta winner in the '90's, turned out a truly wonderful kids' book a couple of years ago. It went one better than his best screenplay and won the relevant category in the Whitbread. Not everyone could emulate that. But it's a great thing to try. Be warned, though. Children have many calls on their attention and make a demanding readership.
For Madonna, of course, this isn't a problem. One of the disappointments of our literary age is that even TV chefs and chat show hosts will always have publishers scrambling. Poor little beautiful works have to take their chance with the rest.
I don't think one should begrudge Madonna a success if the children like the books. She deserves a new career path after making lots of companies & lots of people (and, of course, herself) lots of money all these years. Sure, it's media-savvy, but no one is forced to buy anything she writes.

