For a good overview, get any gazetteer. These usually are 8 1/2 x 11 soft cover (spiral bound?) books with one state to one or two pages. There will also be a small scale map of the whole country spread over two pages. These usually sell for anywhere from $10 to about $25.
Your best bet, from my pov, is join the AAA. Go to an office, sign up for info, and they will bury you in reduced price offers. Or, simply pay the going rate to do it quickly. As a member, you get UNLIMITED free maps of the states. These are very good but do not go down into the county road/route detail. I would call these medium scale maps. For the price, you cannot beat them. Any half dozen maps can set you back the cost of joining, and you get to throw away all the offers for insurance that your membership fee funds. Seriously, there are some good benefits to joining (I've never used any beyond the maps).
The best maps, imo, are the Delorme gazetteers. These are large scale maps that show detail down to county roads in soft cover workbook form (15 1/2" x 11" closed) with one book per state. They sell for around $20 with discounts for multiple maps. Obviously this format tends to be bulky and not mc friendly but the detail is hard to beat unless you go to.....
A computer maping program. You can get all the info above on google maps for free. You can zoom in down to the last alley and driveway in a big city. There are a number of other mapping programs offered by Garmin, Microsoft, Apple, etc. that do the same thing and more, but I'm used to Google. Smart phones offer mapping programs but its hard to see the utility of a 3" x 4" screen/map with tired old eyes (mine) until you try it. These are surprisingly good.
And then there are GPS devices. I use a nuvi (Garmin) for cars on my bike, and love it. I usually back it up w/ handwritten (large, so i can see them while driving) instructions in the map pocket of my tank bag. You can spend as little or as much as you want on one of these, but the better part of a thou for a Zumo is a bit steep for me. A lot of the gps's accept memory cards with your route file on it, but this will require a laptop and software knowledge if you are going cross country.
For my money, the AAA maps are the best bet. You certainly cannot beat the price, utility, and ability to do route planning in any diner over breakfast, or in your tent. If you go the gazetteer route, I suggest you hit a book store and compare several brands.