to get the rounded pages when opening, the book needs to be made in a closed stadium. not a easy task to group, after rigging when opening you get this rounded page effects, so yes it can be closed into zero pose and all is straight, just like real. you only get this realistic effect this way. The traditional way of rigging in poser would not allow this effects as the pages are overlapping when the book is closed simple skinning unimesh in poser makes it possible and the only thing that needs to be done is to smooth out the bending with the joint editor paint tool on the individual groups of the pages.