With the PRS+ addon you can assign a key to cycle through the various booklist options. So when you want to switch from next books in the series to the last opened books, you can just press that key two times.
A new release of PRS+ should come along tonight or tomorrow by the way, which resolves all known bugs, at least for the Book Management addon.
And if there are requests for additional options for the booklist, just drop me a line or post a reply to the PRS+ topic.
Lastly, my appreciation for kpw's great efforts still stands of course, and I will probably keep using this plugin beside PRS+. So no hard feelings, kpw?
