When in the Collections tab, expanding the width of the left-hand column causes the book thumbnails to fill the space of the Collections Pane.
In contrast, when doing the same thing in the Edit tab, the thumbnails for the pages of a book do not expand to fill the allotted space, but remain as a static, 2-column display.
Having a Pages Pane which fills with page thumbnails in the same way the Collections Pane fills with Book thumbnails would facilitate easier page reordering for large books.
The two-column layout is designed to show how the pages will pair up in a booklet (books always show pairs of facing pages). But there may be some way to combine that with taking advantage of more space if it’s available…especially if the book is designed as an ebook and won’t have facing pages.
Thanks John. Strangely, I hadn’t clued into the facing-pages motivation behind that design since I’ve never yet printed a book; I’ve only looked at them on my devices. Now that you mention it, that view totally makes sense which explains why that front cover is up there all by itself… 
Another reason why I didn’t clue into this is that Bloom has a kinda Powerpoint-feel to it which makes me think differently about its interface.
So, I think the facing-pages view is important to retain for print. Moreover, I don’t think it would be helpful to allow the user to accidentally mess that view up by sliding the pane division bar too far to the right.
On the other hand, as you say, for eBooks which don’t have facing pages, a (to use a PowerPoint analogy) “Slide Sorter” view might be quite useful. So, if I figure out how to rename this topic, I’d rename it “Add a “Page-sorter” view to Bloom Desktop”.
By the way, in case it was not clear, you can reorder pages currently by drag and drop.
You just cannot move front and back matter pages.
At least part of a solution would be to make the page pane able to be sized. Zooming increases the page size in the pages/sort pane, but it doesn’t increas the width of the pane. If the width changed then I could increase the size of the thumnails to the point where I can see the content and so allow easier sorting…
Or is there a way to resize the left hand pane in edit mode?