If you're looking for information on the status of Diane Duane's The Door Into Starlight, you've come to the right place.
The book is presently in progress, though DD has stated that she will not be issuing detailed progress reports -- no news about word counts and the like. She will make an announcement (here, and elsewhere) when there's a completed first draft of the book. After that, what happens to the book will depend on her literary agent's advice and on what publishers become interested (or don't). She has committed to self-publish Starlight if there is no interest from conventional publishers.
For more information on the book, its background, and its present status, please start out by reading these articles from DD's blog:
How to find out how the project's progressing:
At the MiddleKingdoms.com website there's a project status page where news will be posted, and you can bookmark/follow it if you like. (We'll also be opening a Facebook page for this, so that people who like the books can get together.)
But probably more effectively, you can also sign up here for the book's dedicated news-and-info mailing list, which is handled via MailChimp. (This is a different list from the general Ebooks Direct mailing list that's offered at the bottom of the page.) If you like, you can click here for a look at a typical newsletter.
One last thing: A dedicated discount still exists here at Ebooks.Direct for those who want to encourage DD by making purchases with the purpose of inflicting guilt on her. The discount code STARLIGHTGUILT will allow you 15% off your purchase. Please note that this discount cannot be used in conjunction with other discount codes: the store can't handle two codes / "coupons" at once. (Sales of items running timed sales or other types of discount are not affected.) Consult the link on how purchasing works for info on where in the ordering process to use the discount code.
Thanks very much for your interest!