I'm an American living in Madrid; bought this book for a driving tour of the north: Galicia, Asturias, Cantabria, Euskadi, and Navarre. I've not yet tried it on the south of the country. I've used Lonely Planet for 10 years and approximately 30 countries.
I found this book to be dissapointing for the following reasons:
1. A lot of info in the book is outdated, like they just left stuff in from 2007 without checking it. It's more than just closed restaraunts and discotechs (although they exist in spades) - there are huge swathes of highway missing from the maps. A lot of this was editorial sloppiness - for example the map of Spain in the front of the book has some of the new highways, but the province maps at the start of each chapter do not.
2. It leaves off Ceuta, Melilla, and the Canary Islands. The Canaries are clearly missing because LP wants to gouge you for a second book (they do a similar scam with the US state of Hawaii), but why are Ceuta and Melilla missing? The book is very preachy about getting off the traditional tourist track, and those two cities (which are Spanish enclaves on the North African coast) have unique cultures and really rely on tourism to survive. It is especially galling bc the book instructs you how to take the ferry to Morroco from Algecieras, without ever mentioning that you can easily go to Ceuta just 20 kilos away on the same boat. It smacked of political correctness of not wanting to offend the 5 Morrocans that might purchase this book.
3. My opinion is that the booked lacked a sense of itself. For example, it might only tell you how to get to a city by bus or train, as if the reader is likely to be a student that is too young/poor to rent a car. But, after "getting there", the accomodation options will center on quaint inns out of town at a price of 120 euros a night, which someone arriving by bus could not reach or afford. Other times the book goes the exact opposite direction, for example by telling you to drive the 5 kilos from Malpica to St. Hadrian when there is a beautiful coastal walk (complete with boardwalks) that passes several sheltered coves, beaches, fountains, and picnic parks, as if only older drivers and never anyone fit would be on the Costa Morte. The book tries to be both "Fodors" and "Rough Guide" at once, and comes off not being as good as either.
4. Far too much space is devoted to food. For example, octopus is the traditional dish of Galicia, but do I really need to know 5 different octopus restaraunts in every city, and 2 in every small town? No one wants to eat that much octopus, and I can just look at the signs anyway. At least for me, I get in the car and drive Spain to see the sights, not to eat stuff that I could just buy in Madrid without difficulty. This seemed to relate to the book's lack of sense of itself - the huge focus on food is clearly meant to appeal to the fat American cruise ship crowd that would normally buy a Rick Steves guide. But it really turned me off as the traditional LP customer (young professional with lots of travel experience). And the vegetarian advice is severely lacking, even where vegetarianism is easy like Madrid. Please LP - less food, more sights.
5. The book alternates between a snide tone and an overwhelmingly positive one, without directly stating the reasons for either. For example, the town of Arena at the base of the Picos is described as "singularly unimpressive". But why? It has a nice river park, plenty to eat and drink, and is the obvious base to start the gorge walks. The real reason is that it is a tourist trap for Madrilenos taking day trips, so there are a ton of stores selling "local artisen" products at a 1000% mark up from the same item in the supermarket 50 meters away. So, why not just tell me that, a la "Note that often the 'local artisan' products are really mass produced items available at supermarkets for substantially lower prices.". I appreciate directness.
6. A minor complaint - the book wastes a lot of space writing out that places are wheelchair accessible. A simple picture of a wheelchair (like a handicapped spot) would suffice. Such symbols are already used for things like accomodation (a house) and dining (a fork and knife), so this is a no brainer.
Rolled together, these issues made the book less enjoyable for me than a typical LP product. That said, it does provide a lot of information and can really guide you through most of the country, hence my "fair" rating. If I had it to do again I would look at the other guides first before reaching for this one, which is contrary to my usual always-buy-LP standard. Happy travels!