The layout book has global view settings for items placed onto the layouts. These view settings include layers and pen set, and once changed are applied to all layouts.
Drawings and Figures placed to layouts use the source view or Drawing Elements pen and layer settings; but elements drawn directly on the layout (Lines, Polylines, Fills, Splines, Text, Labels, etc.) use the layout books layer and pen settings.
Unfortunately there is no direct control for the pens and layers of the layout book. If you notice elements on the layout are missing (hidden layer) or using the wrong pen set as in the following image:
Go directly to the layer or pen settings under Options > Element Attributes. Notice the drop down menu includes “(Layout Book)…” after the normal menu option for these settings:
Changing the settings here changes the Pen Set & Layer Combination for the entire layout book: