It would help to have more information
- Are all your images in one folder?
- Are all you images portrait or all landscape format or is there a mixture
- Do you want them all 8.5 x 11 out to the edge or with a border and also at what resolution e.g. 300 ppi or other resolution
- Do you want the entire image to fit best it can within those boundaries or do you want them expanded and cropped to fully fill the 8.5x11 (or other format)?
The more details you can provided the better the recommended path can be given.
Just a suggestion
All of my images are in one folder. The folder contains 2 separate folders where my images are respectively organized both vertically and horizontally. The orientation of my 8.5x11 pages(for my book) is portrait. I have as well already batch resized my images to fit the page with a border. For vertical I think I sized 10 inches for the height and for horizontal it was 7 inches for the width. All are 300dpi RGB color mode.
Thanks for the info. Apologies because I may have misunderstood your original question. It sounds as if all the files are already processed to the size and resolution desired and you just need to complete the final step.
There are many photo book services out there all with their own way of accepting images. It is also different if you were created a PDF book instead of a hard copy book through a service. Also, some quite old versions of Photoshop had this type of capability.
So sorry for additional questions yet with all the work you have already done, are you heading to a Photo Book service provider or combined file format (e.g. PDF). It is just not clear to me the specific destination of the next step and the version of Photoshop (or feature if old version) you are trying to use. Note that a number of photo book services have a batch upload process yet that is a topic outside of Photoshop.
This also may be so obvious to another forum member (outside my understanding) that they should jump in to help.