Because of legal reasons we can only have books from the public domain. If you know some that are free, just point me to them and I'll match them for you. I need them to be in .epub format for both languages.
We do have a tool that does real paragraph matching based on the Gale–Church alignment algorithm and offline dictionaries. On top of that we have an additional manual process to make sure that the alignment is correct. However many of the books were pre matched and we didn't align them using our tool.