I’m sorry; I don’t know any free apps, but I can suggest two paid apps, if that’s any use.
There’s an app called Audiobook Wizard that I used a year or so ago, under Snow Leopard, that seemed reasonably fast and easy to use.
However, it’s a paid app ($4.99) offered through the Mac App Store: http://itunes.apple.com/us/app/audiobook-wizard/id460967298?mt=12. This is apparently Lion compatible and a decent audiobook editor. I haven’t tested this version though.
The developer also offers a free version, which can be downloaded from his site: http://www.audiobookwizard.com/. This only supports Snow Leopard and below, because it has PowerPC components, but you might like to download it to get a feel for the app.
There’s also Audiobook Builder. Again, this is a paid app ($5.99) in the Mac App Store: http://itunes.apple.com/us/app/audiobook-builder/id406226796?mt=12. I haven’t used this before, and I’m not sure if it’s Lion compatible. A cursory search of the forums on the developer’s website doesn’t find any problems, so it might be ok. Might be worth trying; not sure.
You’re right about .m4a
and .m4b
files. This isn’t so much a problem with iTunes, as the file types. .m4b
files have the capacity to “bookmark” parts of the file that .m4a
doesn’t. From the Wikipedia page on MPEG-4 Part 14:
Audio book and podcast files, which also contain metadata including chapter markers, images, and hyperlinks, can use the extension .m4a
, but more commonly use the .m4b
extension. An .m4a
audio file cannot "bookmark" (remember the last listening spot), whereas .m4b
extension files can.