FREE Barron's AP CSA Test Prep Kindle Book!

I'm not sure why this is free right now, but one of my students noticed that the Kindle edition of Barron's AP CSA test prep IS FREE right now! 

I know many CS teachers teach more than just one course, so I thought some of you might be teaching AP CSA too and might be interested... And/or you'd know others who might be.

(They also seem to have these subjects for free too:  AP Statistics, AP Chemistry, AP Biology, AP Psychology, AP World History: Modern, AP European History, AP United States History, AND AP English Language and Composition.)