"Is this your book"? wrong because of the word order?
Correct. That would be "Er denne din bog?"
Why not den instead Deanne?
That's a difference between "that" (den) and "this" (denne).
So your/yours aren't separate words then? Gender/plurality aside (din/dit/dine), your/yours isn't differentiated?
I believe that's right, yes. Same with "my" versus "mine" and the others. (No difference with "his" because of the 's'.)
I am doing this on a mobile so don't have access to the lessons.
Why not 'den' ?
It would be helpful if the person speaking would brake her reading of the sentence between bog and din so that it is not read as "bogdin".
When do we use din or jeres ?
'Din' refers to one person whereas 'jeres' refers to more than one, i.e. "y'all's".
Is this your book, is the same thing.