Do you own any of the books from the "How to Draw Manga" series?
I got them all

If so, how many? Which ones?
all of them that came out

Do you even use them or did you just get it for the costume and character ideas?
yes

Last but not least, do you work on manga?
still working on that one

I have three of them, though there's at least one other that I'd like to get.

I have the "Male characters" one mainly so that I can figure out how to draw old guys.

I have the "Super Tone Techniques" one, although most of the tones that I use are digital. I'd like to keep reading through this.

And I have the "Developing Shoujo Manga Techniques" one... though I wonder why I bought it.

I've used the male characters ones for hints on simple anatomy. But really, I tend to read them through and then not look at them unless I need a suggestion for a pose or something. I think I should try again... The one I really really want is the Bishoujo Around the World one. So many beautiful women! I have a hard time drawing non-typical looking faces, so I'd like to make my people look like they come from different places around the globe.

I'm kind of working on manga/comics/whatever, but I'm more focused on character design and scripting at the moment.

I buy those. there pretty good when your looking for a new manga style. unfortunantly its not that good. what i mean is that it really confuse some people tho.Your not alone in buyin them.