Very early on in my SIL's journey with this disease i bought The 36-Hour Day : A Family Guide to Caring for Persons With Alzheimer Disease, Related Dementing Illnesses, and Memory Loss in Later Life by Nancy L. Mace.
It was a huge help to all of us, mainly I think for helping to understand how an AD person perceives the world and people around them, what scares them etc. And strategies for communicating, connecting and reassuring them. It also helped (as much as it is possible
) to prepare us for future stages.
That would be my pick, but I see there are some newer titles that specifically cover activities.