Plus points:
o Well written
o Routes accurately described.
Minus points:
o Choice of route... We did two walks from the ten in this book. What I did not realise was that 'muddy' really really really means it. In particular we did a coastal walk featured in the book and ended up a long way from the car walking for about a mile on a track through densely forested country with impenetrable thorny undergrowth on either side where the only way through was 6" to 12" deep in horrible slimy mud for distances of 30 feet or more. You could argue that we should have known because the book said 'muddy' but everywhere was parched and dusty and we foolishly set out in light walking shoes which were fine for 9/10th of the way. Waders and a stout stick or machette would have been more advisable for that part. Believe me, boots and gaiters would have been insufficient protection and you would have been broiled in them for the rest of the walk. Best bet - wear trainers and carry a big stick with wellington boots and a bin liner in your rucsac.
The other walk was better but again led through some horrendously deep muddy patches that my wife at first refused before I pointed out that that meant we would have to walk all the way back.
After that we gave up and planned our own routes using a map which was just fine. What I can say from experience is that walking in Spain is nothing like the UK. In rural Spain there is likely to be an attractive notice board by the road proclaiming the 'muy tipico' walk which after 500 metres is blocked by a barbed wire or a ravenous dog. However, if you go to the high Picos all is well. :-)
Conclusion:
Buy the book but take your wellies and a stick if the walk description even hints at something reminicient of a puddle.