Change media kind of multiple items not working I'm following the guideline in https://www.lifewire.com/create-an-audiobook-from-mp3s-in-itunes-2438719 and have a problem with step


  Use iTunes to Convert MP3s to an Audiobook 
  
  Join multiple MP3s to make your own audiobook


I wanna change multiple mp3 to audiobook. But is not working. Rightclick on selection and "Get Info" -> Options tab -> music-&gt;audiobook from Media kind /dropdown/ and OK. Nothing happens. 

It's works by single item well. 

(iTunes 12.9.2.6 on Windows 10 x64)
If your method does not work it could be the one of the selected  MP3 files (that you are trying to Join in to Audiobook) is not plain spoken word but contains music elements.

I recommend you use the conversion method or find out which MP3 file is the problem.

In this method, you can create audiobook from MP3 files. 

As a mp3 to audiobook converter, iTunes is great. Even though the created audiobook files are deleted from iTunes library, you can import them from local into iTunes or other players with audiobook features. And there is no need to operate on the original MP3 file again as long as you have stored the created M4B audiobook files.

Follow the instructions here ...