Each report involved a different script which until now presented no problems. Experience suggests that this is not an issue with the scripts (since nothing about the script has changed) but with iTunes.

I have not seen this behavior myself, but I have not yet done any rigorous testing. Since I have only received two reports at this point my guess is that this may be a problem with something else and iTunes; a misconfigured plug-in or background app. But that may be wishful thinking and the problem may indeed just belong to iTunes.

If you have seen any behavior like this please let me know as soon as you can. I’d like as much information as possible before I test and eventually report this to Apple.

[UPDATE: see here for the fix.]

This version now works in Snow Leopard but QuickTime Player 7 must be installed–even if QuickTime Player X is also installed. QTPX does not (yet) have the AppleScript support to use this script. QTP7 can be installed from the “Optional Installs” folder on your Snow Leopard installation disc. It will be installed in your /Applications/Utilities/ folder.

tell application "iTunes" to set mute to (not mute)

I’m pretty sure there is no other on-board control to toggle mute otherwise.

It behaves like a track in that it has most of the same properties, can be copied to playlists, and so on. The track kind of a track-that-is-a book is “Book”, at least my Wodehouse book’s is “Book”. Properties that don’t apply to “bookness”, such as start and finish, time, and so on, return zero or null values. Still, some operations you would perform on a music track will error when you run them on a book track, eg: setting the lyrics property.

Books can have artwork. And—perhaps obviously—Books can’t be copied to an iPod/iPhone.

More as it develops.

[UPDATE: the kind of a book track may actually vary depending on the, uh, kind of book. That is, if iTunes "knows" it's a book from iBooks, then the kind may be "Purchased iBook" for all I know.]