If Z-Salem's tip does not sort out the issue, it may be the following, although I don't know how music from CD would be imported as Audiobooks. If the issue is as I have documented, I'm sure we can remedy the situation.
First of all, confirm for yourself whether that the music has been given a genre of audiobook, or a media kind of Audiobook. They are two separate things:
- genre is simply a classification to differentiate between the style of music. Any music file could in theory have a genre of audiobook and still be playable as music in your library and on your device
- media kind is a separator that determines whether an audio file is music or an audiobook. If a file has a media kind of Audiobook, it appears in the Audiobook section of your library and on your device and is completely separated from your music library
Read through the following steps before attempting this, in order to familiarise yourself with which options you will have, dependant upon what you find. I assume that you already know how to switch between the Music and Audiobook sections of your library. If not, see the two screenshots below:

and

You can check the track's information by selecting a track and checking the details for it. Select and then right-click the track:
- if the track is set as media kind is Audiobook, the pop-up menu will have Audiobook Info as the second item on the menu
- the panel will default to the Details tab. Switch to the Options tab
- on the Options tab look for, and change, the media kind to Music (from the drop down menu)
- click the OK button. That track will now move to the Music Library
Alternatively, once you have selected a track, use iTunes' top bar menu to select Edit. In this case, the drop down menu will have Audiobook Info about halfway down the menu list. Proceed as above.
If this is the issue, and you wish to change many tracks in one go, you can select several tracks at once, all of which you want to change in one go, but note that the menu option in both cases will be Get Info rather than Audiobook Info. If files (tracks) were set as Audiobooks, you may find the two audiobook options are on, which you might not want to be on for music. See the screenshots at the bottom of this post for more detail.
However - if the track is set as media kind is Music and with a genre of audiobook, when you select and right-click the track:
- the right-click menu option will be Song Info, about one third of the way down the menu, while the top bar menu will be Edit/Song Info, about two-thirds of the way down the menu
- the genre is on the Details tab, stay on this tab
- look for, and change the Genre to your preference. The Genre field is just over halfway down the Details tab. Change the genre to your choice, either by choosing it from the existing drop down menu, or by typing in a new genre
If you select several tracks at once, the menu option (on both the Edit and the right-click menus) will be Get Info rather than Song Info.
------------------
To summarise:
If imports from CD have been given a genre of Audiobook, they will still appear in your main music library and play as music. In this is the case, simply highlight the songs in question and change the genre to whatever you prefer. Assuming that the songs that you wish to change comprise of several different genres, you will have to identify all songs of a genre, group them and change them to the genre to your preference and then move onto the next genre. Perhaps one album at a time.
But if the songs have been assigned a media kind of Audiobook and therefore appear in the Audiobook section of your library (that is clicking on the menu just below the menu bar of iTunes), then you need to change the media kind to Music.
Finally, there is a difference between audiobooks and music in the Options settings, that you may want on for audiobooks, but off for music. Your choice.
The settings, which are on the Options tab for each track, are:
- Remember playback position
- Skip when shuffling
For Music, you probably want both options off, as shown immediately below:

... but for Audiobooks, you will probably want both options on, as shown below:
