The early sections of the Norte are quite tough, like mikeian said the climbs just keep coming. The beauty of it compensates for this, there isnt too much road walking until you get too bilbao then it builds up for the way to santander and after it. I have never used the CSJ guide, i dont have any particular reason for not using it, and have heard mixed reviews about it , like you have seen in the replies to your post. There is new guide in english coming out in the new year for this route, you may have seen the post from the author in the Norte topics, ive got a feeling its going to a good one. The early sections of the Norte are very busy people have heard of its beauty and it makes for a natural 1 week walk from irun to bilbao.The walk from deba to markina was about the most beautiful i have encountered on any of the routes, a higher walk along natural path in forests. However the trudge out of santander in pouring rain on busy roads next to industrial complexes balances out the beauty. It is a challenging route, not just because of the toughness of the early stages for a starter.