The Blue Ridge Parkway releases a free travel planner seasonally. These useful books can be picked up at any visitor center, and many grocery stores have them in the free publishing racks at the store entrance. This provides a great overview of the parkway.
However, if you plan on doing some hiking, you’ll need something with more detail. We have the larger Falcon Guides Hiking the Blue Ridge Parkway: The Ultimate Travel Guide and the smaller pocket size Best Easy Day Hikes Blue Ridge Parkway.