Well, most of the study manuals are based on whatever the current question pool contains at the time of publication. For technician, the current question pool is valid for 2014 to sometime mid-2018. Older manuals will probably get you familiar enough with the material in order to pass but may not include any material additions, corrections, or if there were regulatory changes.
Personally, I wouldn't get a current copy of the manual since it'll be defunct in a couple of months anyhow. Instead, concentrate on the on the on-line practice tests and use the internet to research areas that you are having trouble with. Repeat until you score 80+% and you will pass the written test with flying colors...