Comprehensive Grammar of Kurmanji Kurdish -- Mustafa Durmaz
I've just learned of a recent doctoral dissertation comprising a comprehensive Kurmanji grammar in English that is now available.
The introduction and table of contents can be seen here, and copies in various formats can be ordered from the same website:
As far as I'm aware, there hasn't been a full reference grammar available in English, although shorter grammatical sketches have been published. I would hope that this will become available as a formal publication at some point, but in the meantime, pdf downloads and hardcopies in various formats can be ordered from the website above.
I haven't seen the full dissertation yet, but am much encouraged by the table of contents, and wanted to pass on the information for others who might be seeking such a reference.