As well as reading, I'm interested in making my own comics, although I've only actually completed one so far (The Gift in 2006). I have several more on my "to do" list, which are at various stages of plotting/scripting, but the main hurdle is my drawing skills (or the lack thereof). In the meantime, I've read various books about the craft itself.
For general principles, the big five are from Scott McCloud (Understanding Comics, Reinventing Comics, Making Comics) and Will Eisner (Comics and Sequential Art, Graphic Storytelling & Visual Narrative). There are others too, but I'm not trying to write an exhaustive list here.
Then there are other books which focus more on the technical aspects. An interesting one is How To Draw Comics The Marvel Way (by Stan Lee and John Buscema). This was written in 1978, so it has to be viewed as a product of its time, e.g. there's nothing about the internet or digital colouring/lettering. If you only read one book about making comics, it should be this one: it covers a lot of ground. However, if you read several books on the subject, you probably don't need this at all, because there are now plenty more on the market which are more specialised. For instance, chapter 3 is all about perspective, but you can get a lot more detail from David Chelsea's book Perspective! for comic book artists. Chelsea's book is pretty heavy going, but it's worth the effort. Another one I recommend is The DC Comics Guide to Coloring and Lettering Comics (by Mark Chiarello and Todd Klein). This is one that's definitely worth buying rather than borrowing: I referred to it frequently while I was working on "The Gift", and I think it will take me quite a long time until I've fully absorbed everything from it.
More recently, I bought How to make webcomics (by Brad Guigar, Dave Kellett, Scott Kurtz, and Kris Straub). This is quite different to the others, because it's not really talking about storytelling technique or technical skills, so there's very little overlap with the other books. Instead, it's much more about the logistics of running a webcomic as a business. That's not something I have any intention of doing, but I'm interested to see how other people handle it, and it's always good to have a backup plan if I ever get fed up of working in IT. For instance, if you get your comic published, where are you going to store the books until they're sold? As Kellett says, "A batch of books have the charm of both weighing a lot, and yet managing to be constructed of the flimsiest material on earth." Similarly, David Willis (from Shortpacked!) recently posted a photo of a literal ton of books. So, there's a lot of good advice in this book, which I haven't seen anywhere else, and I recommend it reading it if you have any interest in the subject.