LrC Photo Books page margins/padding?

You can select photo cells on multiple pages (cmd click on Mac, ctrl click on Windows), and then change their cell padding in one go.

A possible answer is to create an Auto Layout Preset that uses Custom Pages.

My steps to do something similar-

1) Design the Left-hand page as I want: One or more photo cells. With the extra margin down the spine area. You could easily modify one of the supplied templates!

2) Save the Custom Page.

3) Repeat Steps 1) & 2) for the 'Right hand' page.

4) Create a Auto Layout Preset that can populate all photos on the filmstrip into a preformed book by one click of [Auto Layout]. Use your Custom Page templates for a 'Fixed' Left and Right pages. (Zoom to Fit or Fill can be an option.)

5) After selecting your photos and opening the Book Module:

6) Select your new template Preset in the Auto Layout panel and click on [Auto Layout]. You will get an automatic result similar to mine (with Zoom to 'Fill' set in the Preset!)-

My one annoyance of Custom Pages in the Book module is that they cannot be named and can only be chosen by visual appearance in the Page template selections.