High Sierra vs Apple Reader/iBooks

On my souped up old Macbook Pro 2010 15" - I opened Apple Reader after (finally) updating to High Sierra... and it doesn't work. Rather, it reports that "iBooks cannot access your library." And the library location reports as "null."

Anyone have a clue as far as fixing this? Odd that my CS4 Photoshop works fine (after legacy java install) but Apple Reader, which no one mentioned being problematic, doesn't.