In case it's useful to anyone: another implementation of this idea is Weeve https://shop.weeve.ie I bought one of their books (a study in scarlet) but it wasn't great. Lots of mistranslation, especially later on in the book. The general idea seemed to work well though, with better implementation I think it could really help my french.
I'll give this one a try, being able to add my own books is particularly exciting.
I'll give this one a try, being able to add my own books is particularly exciting.