This bookshelf has three geostates, none, 0x4CF9B596, and 0x8A6C4E39.
You have to assign parts of the mesh to each geostate. It's important to divide the mesh into two or more groups in advance.
I divided the mesh (sans drop shadow) into two groups: group 0 corresponding to shelf body and group 2 to books.
In group 0, click 0x4CF9B596 and "...". "Face selector" window pops up. The faces selected here will appear in geostate 0x4CF9B596 in game.
As for how to use face selector editor, please read this article at TS3 wiki.
I always use this setting:
Group 0 is shelf part, and always visible in every geostate. So select all the faces here.
Or in left window, select a whole mesh by dragging square.
Click "Done". Now geostate 0x4CF9B596 was set in group 0.In 0x8A6C4E39 of group 0, select whole mesh in same way.
Go to geostate 0x4CF9B596 of group 2, I want to make only one bottom book visible.
So select it within square and click Done.
In geostate 0x8A6C4E39, make two books visible.
Now all geostates were set as intended.