I think that, like most people, we picked this up in the gift shop after spending a long visit in the Prado. It, like most gift shop items, was a bit pricey but it was definitely worth the cost.
Unsurprisingly the majority of the book is dedicated to Iberian artists, but it also gets into works from other nations that the museum holds. The photos of the art work are incredible, and do a great job capturing the details. The blurbs accompanying the photos are informative, but not mind blowing.
Really the best parts of this book are not the works of art I already knew about (Goya, Vázquez, El Greco, etc.), but rather learning about new artists and themes. Flip through this with an open mind and you will find new and awesome things.