In the book Americanah

Ifemelu is the narrator in the novel. Americanah.

the narrator is unknown. It is written in the third person by an omniscient(all knowing) narrator, meaning the narrator is not Ifemelu, but instead an unknown entity. his is why the book is able to switch its perspective from Ifemelu to Obinze(this is because the book does not use I'', but 'he' or 'she' showing it is third person, and the fact that the narrator can accurately describe characters' feelings, shows they are omniscient).