Track 1 of 1...Cannot change to Track 1 of 12, etc.!

I have a LOT of audiobook CDs that I've ripped to my computer. When I burn the CDs, I join the tracks. So, in the screenshot below, you can see that I have six tracks for the album The Mysterious Affair at Styles. I realized when listening to this book, that every single track is listed as "Track 1 of 1" on my iPod, so I spent the entire morning changing all of my tracks manually via the Get Info button so that they are correct because otherwise, the iPod stops playing after the first track, instead of moving on automatically to the second.(I have verified that the track numbers are also changed in Windows Explorer after I changed them in iTunes.) As you can see in the screenshot below, I have the track numbers all corrected, but my iPod still will not flow from track 1 to track 2. This even happens on the audio books where I *didn't* join the CDs, meaning that an album with 100 tracks will literally stop every three minutes because every single track is looked at as Track 1 of 1, rendering them completely unlistenable!!

It is literally ONLY the items in my Books & Spoken genre that are affected. Items in my music genres are fine. I even tried changing the Genre to something different (or changing the Grouping to the current album for all tracks), but it STILL doesn't work! I just want to listen to an entire album without having it stop after every single track!!

Running iTunes 11.0.5.5.

PLEASE HELP!