I already made a python-script that generates meta-files for pdftk and runs it on every file, but the problem is that pdftk does not seem to support special characters so it's useless for german books ("äöü").
If there is a simple commandline tool that can update the meta-information i can do the "batch-work" myself now.
PS: I like soPdf, though for other purposes, I'll give it a try to prepare pdfs for reading them directly on my Cybook, thanks!
Update: found a way to include the special characters, now I only have to finish my script