grammatical number - What’s the correct plural possessive of “kids”?

I know that children’s books is correct, but for some reason I want to say kids books, even though I know that it’s a plural possessive noun ending in an s.

A quick search on the web turns up Barnes & Noble, who have a web page title that reads “Children's Books, Kids Books”.

Is the major bookseller wrong here? Or is there some exception I don’t remember?

More simply, is it kids books or kids’ books — and why?

Answer

Part of my answer to the question posted here was:

According to ‘The Cambridge Guide to English Usage’, the removal of
the apostrophe from 'plural nouns in phrases which express affiliation

. . . is widespread in the English-speaking world' and has the
imprimatur of the American Associated Press stylebook and the
Australian government Style Manual. As the Cambridge Guide says, ‘the
time spent worrying about whether it should really be driver’s licence
or drivers’ licence would be better used elsewhere.'

Nothing is lost by writing kids books rather than kids’ books. However, the Cambridge Guide does point out 'that there are special cases which seem anomalous without the apostrophe s', and one of them is childrens, 'because that is not a regular form of the word . . . Thus context is the final arbiter as to whether apostrophes are needed, as always.'