I'm wondering if the Western Topo - Eastern map downloaded correctly into BaseCamp. All it shows are the names of lakes, rivers, scant forest types, many horizontal lines, a few major trails, and major roads. It doesn't show any cities or city, streets,minor trails, or topo lines.
Exactly which map did you download? Was it this?
http://www.gpsfiledepot.com/maps/view/300/
I have never used this map, but considering that it shows something like half the world and is only 79MB, I would not expect to see much detail. For example, I posted a topo map of New Jersey here - one of the smallest states in the US - and it is almost twice that big (151MB).
The scale of that nap reads 1M, so it's a small scale map an would have the details of a large scale map such as a 25k map.