Like all of the Routledge Essential Grammars I've seen, the Danish version is quite good - pretty much covering the bases on what you need to know to be reasonably proficient, if not fluent, in the language. Some of the terminology may be a little opaque to people who aren't hardcore linguistics or language people, but it's not insurmountable. I don't think you can learn a language from this, but it's a valuable tool.