Can I revert back to aperture from Photo's?

Ran the Photo's import, initially looked good. But...I have a lot of Photo Books creation in Aperture. This wasn't handled, as nice as I like. Missing pictures from layout or blank chopped pictures.

My hope is they (Apple) will improve the import process in a coming release. In the meantime, I'd like to go back. How can I back out from Photo's, and try the import/convert again in a few months?

If I'm understanding your post, then the answer given in the 4th reply via the following link should be helpful to you.

https://discussions.apple.com/thread/6985941