the self proclaimed "Material Girl," money can't buy happiness.

That's quite a lesson from the 46-year-old pop diva, whose fifth children's book in the past 18 months "Lotsa de Casha," hit store shelves this week.

"Lotsa was by far the richest man in the country. He had everything that money could buy," is the opening line of her latest book. "But there was a teeny, tiny problem. No matter how much money Lotsa de Casha made, he wasn't happy."

The short book concludes with the moral, "When you learn to share, you will not only find happiness. You will also find a friend."

Renowned as much for her catchy dance anthems "Vogue" and "Ray of Light" as she was for cavorting on stage in a partially disrobed wedding gown some 20 years ago performing "Like a Virgin" on MTV, Madonna Ciccone Ritchie said she's left some of her old antics behind and is all grown up now.

"I'd like to think I've been evolving and transforming my whole career, I grew up," she told Reuters in an interview.

"The media likes to say it's just another one of my guises,' she said of her career as an author. "But it's much more deep and profound than that."

Madonna the singer is known as a chameleon, morphing from sexy outfits and suggestive lyrics to Eastern mysticism and Judaism. Similarly, Madonna the writer has penned a series of books which barely resemble each other.

A different illustrator was hired for each of the five slim volumes. But they are all anchored by the same message, she insists: "Nothing is what it seems."

Her intended audience and some critics might agree.

A book reading at a New York bookstore on Tuesday drew puzzled responses from the group of about 25 kids, who appeared to have difficulty grasping the book's morals.

"I think she makes the same mistake every celebrity author makes: They think they can write children's books," said Ilene Cooper, children's book editor of Booklist, the review journal of the American Library Association.

"Generally it's just awful, beyond awful," said Cooper of efforts by celebrities-turned authors.