Straightforward, Descriptive
Tilja is a heroine on the verge of adulthood, who is discovering the world outside the Valley for the first time, as well as her own magical powers. She's got a lot going on in her life, so it's really important for the readers to understand how she thinks, feels, and reacts to different things.
Dickinson depicts Tilja's adventures in a frank manner, telling us exactly what she does and what she thinks, which allows us to really get inside her head and understand all the fun stuff that's going on in there. And while it might seem overwhelming to stay so close to one person, Dickinson always communicates Tilja's experience in a comprehensible way. For example, when Calico gets loose, the way Tilja reacts (physically and emotionally) is laid out for us step by step:
"That's enough of that," called Meena behind her. "We're not doing a ha'porth of good. I've got to go and see to old Alnor, and you'd better do something about that horse of yours."
She was right. Tilja laid her sweep down, hurried forward and grabbed Calico's halter, wrestling to hold her head still and trying to calm her with her voice. No good. The horse was drowning heep in the bog of terror. Tilja's heart began to thunder with the useless effort. Dimly she was aware of Meena groping her way past her, of the cracked old voice starting to sing. Calico gave two more violent heaves and stilled, shuddering. (4.97-98)
(FYI—a "ha'porth" is Old English speak for negligible amount. Bonus points if you can work it into a sentence at dinner tonight.)
Because Dickinson records what's said in addition to Tilja's physical reactions and the way she feels about events, we get a pretty clear picture of what's going on at any given moment. And Dickinson does so while keeping the language pretty simple and straightforward.
Dickinson isn't stuck with Tilja, though. He keeps things interesting by offering lush descriptions of the surroundings as they change along Tilja and Co.'s journey. Check out this passage:
The cliffs dwindled and were gone. The river was far broader, its current less fierce but still easy to see, and they floated steadily on between wooded hills.
There was something else different too. It took Tilja a little while to realize what it was. The trees here were already in young leaf. And the air was warmer, lusher, and at the same time, somehow drier. They were not in the Valley anymore, not even in a place very like the Valley. (4.113-114)
Can't you just see it all in your mind? And all this description does more than just paint vivid scenes for us—it also subtly reminds us that Tilja is a long way from home, that time is passing and things are transitioning, both for our main girl and the world she lives in.