Paris and Normandy

I would read where it says Is This the Right Book for Me?
https://store.ricksteves.com/shop/p/normandy-guidebook

Review his audio walking tours for Paris. Look at Paris-walks and Paris Greeters walks.
In Normandy there are many choices for guides, we used Battlebus tours for two days.

Not that I don’t use his books but any guide book on either place will be just fine for your research.

As described on the link above, the content in the Normandy Snapshot is exactly the same as in the France book. So the difference would be in the Paris content, which is extended in the Paris book (more self-guided tour routes, notes about shopping and kids, coverage of Auvers-sur-Oise and day-trippable chateaux), but still adequate in the France book.

I personally feel RS gives very minimal info on the D-day areas of Normandy—particularly if you are spending five days there. If you are interested in that area, would do independent research about the history and geography of the area. It is a huge area, and there is much to see. But if you don't know what transpired there in 1944, you won't get the best of your trip. Fortunately, this is research you can do before you get there. Read, read, read,...