This is the 548th most frequent Icelandic word.
sjálf
"Self" or "herself" (depending on context).
Here, 'sjálf' emphasizes that I did the task on my own, showing reflexivity and subject emphasis.
Ég leysti verkefnið sjálf.
I solved the task myself.
In this usage, 'sjálf' stresses that she is the one who took the decision independently, highlighting agency.
Hún tók sjálf ákvörðunina.
She made the decision herself.
In this context, 'sjálf' refers to the entity (the book) to underline its intrinsic attributes.