Hm, I just found
this on twitter:
TVアニメ「新世界より」公式アカウント
@shinsekai_yori
ギギギ・・アニメ「新世界より」は、全25話2クールでズラ！( ｀・∀・´)ﾉﾖﾛｼｸ #新世界より
So apparently it is indeed officially 25 eps. And since the recap episode wasn't mentioned among the "officially" counted episodes... it's probably 25 eps of story. Nice, at least it's better than 24!
