Thanks for buying the book! :0)
So "täst" is a property of one of entities? Hmmm not sure I think you would have to ask the Entity Framework team about that one.
I am currently in the process of redesigning the query object to use Linq expression trees rather than my hand rolled solution so this might solve your issues. This will also alleviate the need for a query translator as well.
Check out the project page http://aspnetdesignpatterns.codeplex.com/
, I will update this post when I get the new source code up which shouldn't be too long now.