These kinds of books are always listed months before the next version of Logic appears. They are placeholders in publisher's schedules that are automatically listed on places like Amazon. The books aren't written yet.
There were "Logic Pro X" books listed by publishers months before Logic 9 appeared. The release dates of those books had nothing to do with the release of Logic 9.
Look at this thread from 2007:
Mac OS X Audio • View topic - Logic Pro X Anyone?
Quick summary: "Logic Pro X" books were listed for pre-order in March 2007. Logic Pro 8 was eventually released in September 2007. A similar thing happened with Logic Pro 9.
EDIT: An explanation, here on Gearslutz in 2007, from someone who actually writes these kinds of books: Logic 8 ? *merged*
then i stand corrected...