Reddit reviews Re:ZERO -Starting Life in Another World- Ex, Vol. 1 (light novel): The Dream of the Lion King (Re:ZERO Ex (light novel) (1))

I mean, you could read his backstory novel instead https://www.amazon.com/dp/0316412902

She's From this book! And the Anime re:Zero Ex, Vol. 1 Re:ZERO Ex light novel! This volume was written after the anime and its very, very good in my opinion, Its basically standalone, And its pretty tact with Ferris as a character, And its the one where she's revealed to be trans

It's a light novel spin off so i'm not sure you'll be able to read it online but I was able to get it off amazon

Ferris's Book

Here

I'm honestly kinda surprised they're translating the Ex novels as well, which is nice. That kinda increases the chances for them to translate the Tanpenshuu ones as well (I hope).

It's Re:Zero Ex
(Amazon)

Re:Zero EX1 is about Ferris and Crusch's past. It's a novel which has been officially translated: https://www.amazon.com/Re-Starting-Another-World-light/dp/0316412902/

The part where Crusch finds Ferris is not in the volume, but instead in a separate story. Part of that story has been translated (the part where she finds him) and I'll link it to you once I find it. I don't have a link to it right now.

Here is a part of "The Successor of Blue" short story. Ferris gets the title "Blue" in this story. Only a part of it has been translated:
https://docs.google.com/document/d/1Tm3snQj19e0da7k8tK_W0_7R45-z8-DwQlUuNrw4svQ/edit

There are also more short stories about Ferris, but they haven't been translated. Not even parts of them.

https://www.amazon.ca/dp/0316412902/ref=sr_1_1?ie=UTF8&qid=1494880102&sr=8-1&keywords=re+zero+ex

If you are interested to read more about him, Yen Press is releasing the Re:Zero EX novel on November 21 (so in 3 says) that has the basement thing, etc. in it. https://www.amazon.com/dp/0316412902

Well then, I don't know if you are interested in reading, but do you know about this? https://www.amazon.com/dp/0316412902