#croceting

I am attempting a blanket that is solely a single crochet. That's it. Just repeating a single crochet over and over.

My book(let) says it should look like this:

This is what mine looks like so far. (Excuse the bad lighting and my legs)

I'm assuming these are the two loops I'm supposed to be going through:

Basically, the two along what I'm thinking of as the 'spine'.

In my yarn in this particular section, both of those stitches/loops are blue. BUT am I supposed to be hooking the purple that is over the front from the previous row and ONE blue, not both blue?

I'm just very confused, because while it is solid (and tight, I crochet tightly no matter what size hook I'm using) it does not look like the example.

The whole thing is the full spread of my arms (not tightly, I can't hold it taut that way) and if I'm misunderstanding, I want to know before I get too far.