There's going to be a new book put out collecting 2nd Age material, aimed at Amazon viewers, but it won't be out before the series starts, sorry to say: https://www.amazon.com/Fall-N%C3%BAmenor-Other-Second-Middle-earth-ebook/dp/B0B1DVP4J3/ref=tmm_kin_swatch_0?_encoding=UTF8&qid=&sr=