When I read a book lying around, I get the option "Take" displayed with the key "E". However, I can't take the book by pressing "E", or any other key, for that matter.
Should just be the action button. Press it once on a book to get the book up to the 'reading' position, and then it should say Take/Steal in the bottom right corner.
Found the solution: When you change shortcuts, that change is not reflected in the shortcut hints that are displayed (i.e. it always says "Press E", not "Press Activate", even if I changed the shortcut for "activate"). But it expected the currently assigned shortcut to be pressed.