A "wonderful" book for teenagers is going to waste due to censorship, a former teacher says.

Betty Robb, 76, borrowed Into the River by Ted Dawes from Glenfield Library in Auckland and was told by staff it was restricted to readers aged over 14.

Betty says the librarian then added insult to injury by telling her she was not allowed to lend it to anyone under 14.

"It is probably easier to steal a car and go for a joy ride than borrow a restricted book."

Into the River is a coming-of-age novel that sees a 14-year-old Maori boy struggling to find his own way while battling with his cultural identity.

He moves from small-town rural New Zealand to a prestigious boarding school in Auckland after winning a scholarship.

Into the River was named book of the year at the 2013 New Zealand Post Children's Book awards.

The book was submitted to the Office of Film and Literature Classification in 2013 and initially classified as unrestricted.

The classification was reviewed by the Film and Literature Board of Review after a request by the Family First organisation and amended to R14.

Betty says teachers and writers have made great strides to engage boys in reading.

"I would be happy to read this super book to any young man…boys mature a lot earlier these days and are more worldly wise than we ever were."

Libraries and information general manager Allison Dobbie says Auckland Libraries agrees wholeheartedly with Betty.

"Into the River by Ted Dawe is a book that should be easily available to young men to encourage their reading. This is specifically the audience that the book was written for."

She says a number of library organisations, including Auckland Libraries, disagree with the censorship and have recently filed papers to appeal the decision.

Betty and her husband, both teachers, spent years teaching in isolated districts in New Zealand.

She says whoever decided on the censorship has probably never lived and worked in the same kind of places as her and the author.

"I would have been very disappointed if I had written the book with such great appeal, only to have a censorship slapped on it. What a waste of effort.

"It seems to me that teenagers can access on the web far more rude material than they will ever find in Ted Dawe's book Into the River."

Allison says due to the book's classification libraries are not able to place copies on open shelves and the book has to be clearly labelled to make the restriction clear.

"We are obligated to apply censorship decisions even though this is often difficult administratively and from a customer perspective, as penalties can be applied."

*This story has been amended since it was first published to correct an error in detail around the classification process.