Mike Kamermans over at NihongoResources.com has been working on a project for years now. In all likelihood, you’ve seen his site and you may have even downloaded his book-in-progress. It is a comprehensive book on Japanese grammar and available here to download for free. He told me he is almost ready to publish a non-digital version* and would love any comments or corrections.
What are you waiting for? Download it, grab a cup of coffee, and read!
* You know, the kind you can actually hold, see the ink, and smell the glue in the binding.