I have seen Dragon used once, and though it made a mistake here and there, it seemed decent enough. Fixing things by voice command seemed more arduous than by typing, though (which you can do as well). It wet apeshit when I had a go using the settings of the previous person (whose voice an accent are completely different from mine), but you are unlikely to have the same problem. Apparently, it learns your voice over time as well, which ought to improve results in the long term.

How will you deal with lines? Will voice recognition know which of your speech pauses are at the end of a book? Or do you need it to have some kind of carriage command it recognizes vocally or otherwise?

I don't really see what voice recognition gives you that makes it easier... after all the data entry aspect is only one aspect of it. You'll want to do something with the data afterwards right? And using voice recognition should be worse in the long term (my humble opinion).

I understand your concern with languages, you being in Switzerland, and that both worsens your chances of efficient voice recognition and finding adequate existing databases.

Still, I think the existing database route is probably the least cumbersome overall. You "just" need to find some bibliophile community, or talk to local librarians, about the software they use and try to get your hands on some less-commercial version of it so the license fees don't kill you. A bit of extra investment to kick it off but I imagine then it would be much smoother going and with data which will be adequately structured for further use.

If you figure something out do tell. I have an Access DB I update manually as I buy new books with titles, ISBN, etc... One of my peeves organizing has been that I read in EN, FR, PL, ES and PT :)

My Day Job office uses Dragon Naturally Speaking, aka Dragon Dictate, by Nuance. It's a reasonably-priced, relatively inefficient gumper of a program that is really irritating about updates, which frequently don't register for whatever reason. It is also a pretty remarkable voice dictation system, flexible and easy to use. It does not require a sound card or any special hardware, and most editions come with a headset if you don't have one already.

The problem you're going to run into is that it won't know how to spell a lot of names, but it has a voice-activated "Spell" command, so for names you can tell it to enter spell mode, spell the names (same with obscure words), and then go back to regular dictation. It is extremely flexible, and probably the best on the market right now.