This is the 698th most frequent Icelandic word.
opna
"Opna" means "to open" in English.
The word 'opna' is used here in its literal meaning, depicting the physical action of opening an object, in this case, a door.
Ég ætla að opna þessa dyr.
I am going to open this door.
The word 'opna' is used here in a metaphorical sense to describe the inauguration or establishment of a new business place, specifically a restaurant.
Þeir opnuðu nýjan veitingastað í síðustu viku.
They opened a new restaurant last week.
The word 'opna' is employed figuratively here to express the broadened understanding or awareness brought about by reading the book.