It’s a little known fact that Overview has several keyboard shortcuts to make navigating through your documents even faster:
j, k — view next and previous document in the list.
arrow keys — navigate through tree. Selects parent, child, and sibling folders.
u — go back to document list, when viewing a single document.
Both of these sets of keys are essential for rapid review. You can select a folder, press j to read the first document (which automatically switches from the document list to the single document view) and then press right arrow to go to the next folder in the tree.