I used a 2015 Destroyer to study for a DAT taken in 2016. Scored competitively and got into several great schools. I'd recommend getting the newest version, as it will include the most up-to-date info, charts, explanations, etc., but if it's just 1 year behind, you should be golden (based on my experience).
I have both 2013 Destroyer and Math destroyer along with Kaplan study books I am trying to get rid of. I used them to take the 2016 DAT and scored well. PM if you are interested.
If you're not sure you want to invest in the question book, theres this new app thats free and full of practice problems. you should check it out. It's called Flash Educational. https://itunes.apple.com/us/app/id1190200588
It's a great app that lets you kinda study on the go