Hey! Welcome to my secret Case Files page, oooh!
Case Files is a loose spinoff of Fate/Zero, and functions as a sort of excuse to build upon characters and concepts referenced (and then subsequently neglected) in other Type Moon series. Case Files is near and dear to my heart, and despite being a niche hit-or-miss spinoff series, I'm always ready and willing to push that shit on unsuspecting bystanders. At this point, I'm here for sheer love of the game. For further reading on my deep and complex feelings about Waver Velvet, check my Waver Shrine.
Volumes 1 through the first half of volume 5 translated by Twilightscall
The second half of volume 5 translated by Kneenaw
Volume 6 through volume 10 translated by AZ.
Vol 1-10 PDFs compiled by ProtoformX
The manga has had a bit of a troubled history, in terms of English translation. As such, the quality of the translation and visuals can be inconsistent between chapters.
Currently, the manga is being translated into English by UMD and is hosted on mangadex.
I'm SO happy you asked.
First of all, there's the anime. It's not very good, but I had a good time with it. You can watch it on crunchyroll, I guess.
There's also the musical adaptation of the first novel, which can be watched here. Please probably don't post this link anywhere too public. This upload has no English subtitles, but it's easy to tell what's going on if you've read the first case, and the songs are fun. The musical fucks. I love the musical.