MP3Tag does a pretty darn good job of automating the process. If you have a very consistent format on your filenames, then you can tell MP3Tag to use pieces of your filename to build the different tags. For example, if your filename format is Artist_Album_Disc_Track_SongName.mp3, then you can use the "Filename->Tag" function like this: %artist%_%album%_%discnumber%_%track%_%title%.mp3
It will grind through all the directories you tell it to use.
MP3Tag can also use database sources like freedb & Amazon - but I've never had great luck with that feature - I think there's too much cr@p in the freedb database for the matches to be consistently correct.
That sounds pretty good. I should have a look at it.
BTW, I envy guys who can concentrate on audio books. Each time I listen, it ends up with me losing focus for just a second, making me wonder what I just missed, and of course this thinking makes me miss again, and now we're on a slippery slope here. Aggravating, to say the least. I do however like to read though, especially on the subway if I get a seat and I don't have a coffee in my hand. Mostly on the tablet, because books are just so much more available in digital format nowadays. Most of the books I want to read are just one pirate bay, or apple/kindle bookstore, away.
Audio books makes me wonder when someone is going to be foolish enough to try comic audio books. I'd buy. Once. For the laugh.