Stitch Confusion

I've reached the end of my first leg, and am about to embark on the heel. I'm still worried about running out of yarn. I'm also confused. While the pattern looks very nice, it doesn't look like the picture in the book. I'm not redoing it, because there's nothing wrong with what I've got. But I wouldn't mind knowing what I'm doing wrong. The stitches of my sock run diagonally, so they spiral on down the leg. The photo of the socks in the book doesn't show this. Clearly, there's something wrong with my SSKs (I think). But I can't imagine what. I'm pretty confident that I know how an SSK works, and in all other contexts, it seems to make the stitches lean the way they're meant to, on sock decreases and such. So I don't get it. Maybe it will become clear in the fullness of time when I complete the sock, or start the next one in the next day and a half to keep up with my Olympic schedule. < end irony, sarcasm>