Volume 9 of Tappei Nagatsuki's Re:Zero light novels is out on September 25th (volume 10 follows soon after on October 25, 2016). "However, It's Just a Story," the episode 25 finale of the White Fox's Re:Zero anime will be broadcast September 19th. The interesting thing about this is that the anime ran out of light novel material in episode 24. Meaning, as series Twitter points out, anime viewers will be getting dialog and situations for the first time, beating the light novel readers.
It's worth noting that there's a web novel version of the story with arcs 4, 5 and 6, but, essentially, the anime and manga are based on the light novels.
文庫「Ｒｅ：ゼロから始める異世界生活９」の口絵イラストがこちら！ あれ、この状況、台詞、見覚えがあるような……。つまり――現在TVアニメが原作文庫を追い抜いています。ということで来週放送の第25話はまだ原作文庫でも未公開の内容！ pic.twitter.com/vAZNtDeRsj— 『Re：ゼロから始める異世界生活』公式 (@Rezero_official) September 11, 2016