If you are in the Print BOOK module (correction), Contact Sheet, and Zoom to Fit-
You should not see the white unless your images actually have the white areas in the photo.
Is your PS action creating jpg files with the same aspect ratio? and making the white areas part of the image? (jpg files can not have transparency)
Making the files "zoom to fit" is not an accurate representation of the image since my purpose is to make a proofing booklet.
My old action was the "Contact Sheet II" in the old versions of photoshop and then used the layered psd file to add a background, stroke, and drop shadow to my contacts on a 3x3 spread with the file name under it.
There's no simple layout in the BOOK module like there is in the PRINT module, unless I'm missing something.
While in the PRINT module, users have the option to change the background color which is great and the cells are transparent.
But when the image is put in the background, it appears to be something the Lightroom programmers did not account for...
Yes - I now see your problem. I also get the white edges to the photos using the Print module.
Definitely a suggestion for the Lightroom programmers to look at.!
The Book module has some custom 'Multiple Image" page templates, but I have found they are very hard to alter to my requirements. But if you persevere and have a book page that looks good, immediately save it as a custom template you can use always.
The adjustments you can make are 'Cell Padding' and adding 'Photo Text'. The problems are that you have to select each 'Image' cell and each 'Photo Text' cell individually to define them. I have tried holding [Ctrl] to select multiple cells,and that works- sometimes!.
I just tried selecting multiple 'Photo Text' cells and setting them to "Filename" - did not work for some reason (i couldn't get the filenames to show)
Apply your background image globally- that could be your logo graphic
So the best you can do is- Create the best page template you can, saved as "Custom", set a book preset to use only your custom page, Then you can add hundreds of images to the book and get multiple pages of 'Proof Pages' with Autofill. You have the choices- sent to Blurb, JPG, PDF.
I've worked with the BOOK module too trying to get a custom layout, but its so clunky compared to the PRINT module which makes it so easy.
Putting one image at a time is not something I can do at my studio when were working with 52,000 images every wedding season
If Lightroom moderators or watching this, let's get the glitch taken care of!