Dialogue: A Socratic Dialogue on the Art of Writing Dialogue in Fiction (Elements of Fiction Writing) - Lewis Turco
This was pretty decent.

I thought the book didn't really deliver what it promised on the cover (i.e. "How to get your characters talking to each other in a way that vividly reveals who they are, what they're doing, and what's coming next in your story"), even if it did have some useful information. Most of the formatting/grammatical issues that it covered I already knew about, which is why I didn't pick out a book on dialogue's structure and where to put quotation marks, etc.

I was very glad that it covered things like adverbs and unnecessary words that mark out a newbie writer. There were some concepts and issues very well-explained here, and I was grateful to have read this for those reasons, like how the use of dialect in dialogue has changed over time, and about what's acceptable nowadays. That was so interesting.

And I loved that that the book was written using dialogue. So clever! It was a bit unnerving at first, but I grew to love it, actually. I didn't like the book's slightly sexist tone, though, or its tendency to accentuate stereotypes--especially gender, cultural, and classist stereotypes. That's something you really shouldn't do in your writing . . . maybe he should've mentioned that. Or explained that the book was an example of that as well.

Anyway, it was interesting at times, but I don't think I'd necessarily recommend it.