Hi Justin —
You should be just fine studying with the 2013 version —
The biggest difference is that the Trainer got a significant proofread before the 2015 version —
If you have an earlier version, you may notice a few typos here and there — nothing that states a wrong answer or anything like that — but typos nonetheless — other than that, there are no significant differences to consider —
And yes, I recommend you use the book in conjunction with one of the newest schedules —
Good luck studying for the test — get in touch if you need me — MK