I'm traveling trough Asia right now and i use MapsWithMe on both my iPhone and Android. I have to select which country i want to download and after a usually short download i got all major roads in the selected country. A country like Laos is 2Mb, but the country has few roads. Norwegian map is 50Mb++
The app is quite simple though. It show where you are trough the GPS and the map, thats all. Its really quick and 100% offline. I use Airplane mode for long treks on bus to save battery
They have versions for Android, iPhone, iPad, iPod and Amazon Kindle Fire.
I have tried the free Locus, but for me its just to bloated. I only need map.