This is knit in the round, once you have done the cable part that sits on the shoulders. I really think that the pattern should ask for provisional cast on and kitchener stitch. I knitted the cable then sewed it together and it was messy and you have that seam lump.
I didn't take it back, instead I grafted it together as neatly as I could. Not by any means perfect but a lot better than having a seam. Especially since the join is not going to be either in the middle back or at the side. It will be lined up with the sleeve seam at the back, unless you are a whizz and calculate to perfection. (Not me!)
My stitch pick up for the body was a little messy, but I managed to tidy it up afterwards. I knitted the body as written, however it was longer than stated in the pattern, which is fine by me as I added to this too, instead of 8 1/2 inches I made it 11, then did the cable rib.
When doing the sleeves I didn't do the cast on 6, I picked them up from the body instead. Decreased down to 42 stitches and did the rib. If I did it again I think I would go down to 48 and then make a longer rib for the sleeves to match the body.
I knit the neck up as the pattern asked, but it was so wrong for me. There was to much bulk there and it looked just plain weird. So I cast on 11 sts per cable pattern repeat, did the decreases in every 11sts repeat instead of every second one, until I had 3 twists and then cast off. No high neck for me, I can hardly bear things touching the front of my neck.
Looks a bit odd in the photo, but it's a good fit and very wearable.