Tokyo, Japan(CNN) -- Japanese Prime Minister Naoto Kan is used to political lashings. But the latest one is not from an opposition party -- it's from his own wife.
In a book released this week titled, "What On Earth Will Change in Japan After You Become Prime Minister," first lady Nobuko Kan writes bluntly about her husband's shortcomings.
The book says the prime minister is unable to cook a simple meal and has no fashion sense.
But it's the blunt review of her husband's ability to govern that will raise eyebrows.
She writes that her husband -- a grassroots politician -- is a good off the cuff speaker and is suited to working in supporting political roles. But as the world's second-largest economy's prime minister, she questions, "Is it okay that this man is prime minister? Because I know him well."
Nobuko Kan says that her husband has trouble reading prepared scripts.
Of his policy speech as prime minister, she writes that she couldn't give him a passing grade for his delivery.
The marriage between the Kans spans four decades, and is widely regarded by the public as a pairing of equal minds. The prime minister speaks publicly about his sharp-tongued wife and how she is his toughest critic.
In her book, she notes that most of their conversations are about politics. They disagree and debate the issues, she writes, from capital punishment to tax reform.
The book is selling fast at a bookstore in downtown Tokyo.
Yuko Soma, editor of Gentosha Inc. publishing company, says it issued 15,000 books for its first edition that went on sale Thursday.
Sales have been so brisk, the company was publishing a second edition of 30,000 books, Soma said Friday morning.
By Friday afternoon, Soma called CNN to say the publisher was boosting the second edition print to 60,000.
Soma said the initial idea for the book came from Yusuke Nakagawa, an author and lifelong friend of the Kans.
Nakagawa helped Kan come up with the idea of a "spicy tell-all," Soma said.
Japanese voters may not react badly to this unconventional turn by a first lady. The last prime minister's wife, Miyuki Hatoyama, was embraced by the public for her quirks. Hatoyama wrote that her soul rode on a triangular-shaped UFO and went to Venus, which was very beautiful and green.
On a Japanese talk show, Hatoyama also claimed actor Tom Cruise was Japanese in a previous life and Cruise would know her if they met. On the same talk show, Hatoyama said she and her husband get energy by "eating the sun."
Japanese voters took the eccentricities in stride, disapproving of then-prime minister Yukio Hatoyama for his policies, not his wife's quirks.
Prime Minister Naoto Kan appears to have been left out of the writing of his wife's book.
Talking to reporters, the prime minister joked, "I'm afraid to read it."