In one sense, Americanah tells a single story, that of the enduring love of the central character, Ifemulu and her teenage boyfriend Obinze, ('The Zed') but from this central strand Adichie spins much more - keen and often funny observations on race in America (Ifemulu 'becomes black' on arriving in the US) and Britain, sharp descriptions of contemporary Lagos, blog entries and literal strands in the form of a recurring scene set in a hair salon in Trenton, New Jersey. In the latter, Ifemulu's uncertainty about her own identity is to the fore. When she returns home, cultural and romantic uncertainties provide the climax of the novel: "She was no longer sure what was new in Lagos and what was new in herself".
Americanah could have done with tighter editing, and the ending seems both hurried and predictable. But don't let that put you off: it's very enjoyable.