While the Interstates might get you where you're going fast, it's definitely comes at a price. As long as you are on the Interstates, everything looks the same--there's your basic Walmart, Home Depot, Burger King, Pizza Hut, etc., etc. Sure it's convenient, but there's no regional flavor, and after all, that's what you're traveling for.

Some books that might help plot a better route are:

Road Trip USA: Cross-Country Adventures on America's Two-Lane Highways

National Geographic Guide to Scenic Highways and Byways

The Most Scenic Drives in America: 120 Spectacular Road Trips

Remember, it's the journey that counts!