AAHP 14th Edition or 15th

I bought the AHPP 14th edition to study for the all of my ARE 5.0 exams. The NCARB resources said 14th edition and 15th, so I assumed they were similar and bought the 14th edition. Turns out the two editions are quite dissimilar. Can I still study based off of the 14th edition? Or should I buy the 15th edition?

Is there a lot of difference in content or is it mostly just reordered? 

Thanks!