In reply to Stichtplate:
The most standard route, starting in st jean pied de port and ending in Santiago de Compostela via Pamplona, burgos, and leon is a very sociable affair with lots of pilgrim infrastructure along the way (wine, comfortable places to stay, cheap eats, English speakers, shops, waymarking). However there are stretches of flat drab walking in there for sure, and if you go in the best time it'll be pretty busy with other walkers.
The book by John Brierly was fine for me, but if there is a Cicerone book for the route I would expect it's superior.
Any time early or late summer is probably best (april-may or September-october) as walking in Spain in mid summer would probably be brutal.