BPP Textbook Date Clarification

Is there any reason why one should stick to study texts that are marked for a current year exams? For example, I saw a BPP study text on Amazon that is marked “For exams from 1st September 2016 to 31st August, 2017 and was wondering whether I could prepare from this text and sit exams BEFORE September 2016.

Unless I am missing something here, I thought I might as well use the September 2016 to August 2017 study text towards exams in April 2016.

Also, would there be any harm combing the above texts with a slightly different dated revision kit? For example, will a revision kit of 1st September 2015 to 31st August, 2016 go with a study text of 1st September 2016 to 31st August, 2017?

Thanks for your clarifications