I have not found what I consider a good MDX book that seems to focus on writing MDX queries for SSAS. Even one closely titled to that, something like "Writing MDX queries for SSAS 2008" was primarily focused on just writing MDX queries that produced fixed results. In my view it's a niche that some qualified person should fill (or someone can point me to a good book that focuses on MDX for SSAS which really deal with that subject).

Assuming no one can come up with a specific book that meets your needs, I would still suggest MDX step by step which is good for getting a grounding on MDX writing. I also found the MDX Cookbook to be a good source. The MDX chapter in the Expert Cube Development book you reference does have some useful information. I found it very useful to help with understanding how I could use scope for formulas that would have an NA at higher levels.

Hope this is enough to help, assuming no one know of a book I'm not aware of.