To Do

Constraints
- Thumbs: no zoom, no pan
- Scroll: can't zoom out much, can't pan up and down
- Book, Page: just the shown item
Consistent height for all pages (rather than width)
Make sure adjacent pages aren't visible
Thumbs hover and active state (SVG overlay?)
Resize on window resize
When going to thumbs, scroll to the proper part of the page
Show/hide pages?
Support 400+ page collections