Finance Act 2011 will be applicable for May 2012 and Nov 2012. So in my opinion, if u have book of May 2012, then there wont be any need for nov 2012.
But, u have to refer RTP of nov 2012 which gives recent case laws, recent notifications and amendments. Its a must. Its better to refer may 2012 RTP also.
You dont need to buy amended version of Bangar for Nov 2012 if you already have May 2012 version since amendments in Direct Tax Laws are very few. VG sir has uploaded amendments applicable for Nov 2012 on his website you can download amendments from there or you can get amendments in RTP for Direct Tax Laws !!