Rother, rother and rother. I just don't like to browse Cicerone books, Rother are better. But the best to me are that they really select the best routes IMO. I haven't been disappointed so far, bought their books for France mainly, but also Sweden, Norway, Italy... For Norway they just have this one in English : https://www.rother.de/rother-english%20 ... h-4807.htm
but if you don't mind translating the German books, they have just about every region for Norway : https://www.rother.de/rother%20wanderf% ... n-4464.htm https://www.rother.de/rother%20wanderf% ... e-4436.htm https://www.rother.de/rother%20wanderf% ... e-4435.htm
I've found that info is very poor once you get into Norway, even in tourism offices. They often just give you a leaflet with a general map, and hikes from hut to hut. But they don't have day walks for people here just to explore quickly before moving on to the next area. So when I went into Rondane National Park or Dovrefjell–Sunndalsfjella NP, areas not covered in the English Rother book, I just had to improvise. I basically just walked as far as I wished on the classic trails leading to the huts and turned back. But Rother show you a mix of day walks and multi day walks, with very good info. I found their difficulty ratings in Norway to be on the cautious side. A difficult walk in the French Alps on a Rother book is much harder that a difficult hike on a Rother book for Norway. Mountains are simply much older and flatter in Norway, you rarely encounter steep dangerous trails. Most of the danger, from my experience, came from changing weather.