This book is cited in nearly every more recent book I've read that addresses grammar instruction, so I had to read it. Not a read and apply type of teacher book, but it definitely addresses theoretical foundations behind grammar instruction. It does include some application with sample lessons in the appendix, although if application is really all you want, I would look elsewhere (Jeff Anderson or Janet Angelilo). Still, it was a good read if you want more detailed information on research and theory. The chapter that compares behaviorism with constructivism along with Hunter's lesson design vs. mini-lessons (a la Calkins and Atwell) was fascinating.
I really, really dislike Weaver's view on the importance of teaching grammar in schools. I, like Weaver, believe that reading and writing is an incredibly important tool for children learning to write. However, she puts NO premium on learning grammar. She finds it absolutely useless. I do not agree with this outlook. The book has a good section at the back containing potential lesson plans for mini-lessons; these are quite useful if you're going to teach. But otherwise, the book isn't that great. I don't recommend it.
Teaching grammar is probably the hardest and most neglected aspect of being a high school English teacher; mainly because it bores the kids and treats language as a set of rules rather than the fluid concept that it really is. Weaver's adherence to Whole Language is problematic, mainly because so many of our students do not speak English at home and therefore do not have equal exposure to the language.
Some of the methods would be helpful in a classroom, but Weaver claims that Whole Language is backed up by linguistics, which I don't believe it truly is. The research she presents is sketchy, as well.
The first half was very droll but the second half gave good insight and ideas for teaching grammar in English classrooms in a way that students can actually use it.