Hi Liana
I started off the Norte without a guidebook, i think i found this site 3 weeks before i was due to walk, and read a thread saying it was possible to walk it without one. What i would say from my own experience is that it is possible, and it makes each day a totally suprising experience. However after walking with a german couple for 3 days near the end of the 1st week, i was very happy and relieved when they gave me their stein book(outdoor guides) after they had completed their time on the camino. I dont speak german, but just being able to look at the indications of accommodation, distances, services helped me a lot.
Im not sure what the CSJ(eric Walker) guide gives on its pages, i think very basic route information and a few details of accommodation and services i would suggest that you purchase one. The Norte is a lot more difficult from a finding directions point of view than the Frances and with the ongoing construction of a motorway across the western coastal section of Austurias and Northern Galicia there may be whole sections of the Camino markings that may have been erased and not replaced yet, it was that way when i walked it in july 2010.
There will be many days when you you can follow the yellow arrows with few problems, maybe a little shoulder shrugging, and other days when you will wish you had got a guide, but maybe that is part of the adventure and the experience for you if so good luck and Buen Camino.
Mike
Good luck