A thread that might help with your rivers: http://www.cartographersguild.com/tu...ght-place.html Extremely helpful!

As for the rest of your map: I think it is quite nice, but somehow it does not resonate with me. I cannot exactly explain why, but the placement of your land seems a little arbitrary to me.
The style looks good in my view... I like the muted colour of the land as well as the forests. On the other hand, you said that this map is meant for a book. Perhaps some style that is printable in B&W might be better suited?