I found Hourence's book on How to Break into the Industry far more interesting than the first one, because it felt like the points mentioned were actually "applicable", practical. That's what I'd criticize in the case of almost every game/level design book: they rely too heavily on generalities to fill their pages, but I've yet to see a book that covers any given subject fully. For instance, I'd like books that focus on the composition involved like teaching you all about colors, lighting and shapes and how you can assemble them to give a level a soul, or all about scripting and how to pace a level, etc. rather than have all these themes only briefly mentioned in a single volume. (Although as Steppen said, their authors have the excuse of most of the advanced stuff depending on the engine/game)
In the end, you have to move to other books to dwelve deeper into these concepts, so level design books seem to basically serve as simply a ramp to get to higher things. I'd suggest you get one of them, possibly Game Level Design (because it's well-done, and gives plenty of advices concerning documenting and planning levels) or Hourence's HAWOLD and then widen your horizon by looking into other mediums and inspiration sources. As the others said, architecture books, for instance the work of Francis D.K. Ching or architecture mags are great to give you material for your future creations, and photography books can be great inspiration tools (but there are many free websites such as Flickr where you can find similar stuff, if you can put the garbage aside to find the gems).
That said, I read many game design and level design books a few years back and I don't regret it: even though most of them feel like exploiting the beginners out of their pocket money, they still provide valuable advices that save you time along the line. It's basically: others have been there, made the mistakes, why not listen to them ramble about it so you avoid falling into the same traps? The real question is whether it's worth the money, cause after you've been creating levels for a few years, most of what you'll read you already know.
There are also great articles to be found online stuff more advanced than you might find in books (for instance, there's an article on Gamasutra mentioning all the techniques to guide the players through levels, I'm surprised this wasn't part of any of the books I remember reading).