I have not read
Americanah yet but in a fit of trifecta madness I bought it recently (I already had
Purple Hibiscus) and have just scanned it. I can't comment at all on the quality of the storyline but it did seem to me that maybe the prose is not so easy flowing as
Half a Yellow Sun, almost as if Adichie was trying too hard - those only impressions from a quick scan of
Americanah, but enough to put it a bit further down my to-read list than I had originally intended.
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I have now finished my reread of
...Yellow Sun and liked it again, one of the better modern novels I have read and in my opinion worthy of its good reputation and reviews (it seems to me ALL modern novels get glowing reviews, regardless of merit

). I think the Wikipedia page on it is a pretty fair brief roundup of the storyline and characters as I saw them to be. It also sets out the themes in the book; my view is that in the book the themes are handled in a subtle way and do not come across to me as strident propagandizing, or as seeming from an immature student politician as some of such themes can be by those who see everything in black and white terms or who set out to seek to be offended in their pet missions by others in any way they can be.
It was interesting for me to compare and test some of the politics and identity themes, as expressed by the opinions of the characters, with modern day Nigeria 50 years on where ethnic and religious violence is still commonplace, for example Islamic terrorism in the North and just a few days ago religious/ethnic violence killing over eighty persons in central Nigeria.
One thing I felt was that in the prewar years she did not make much of the divide between village life subsistence living and the life of the privileged (in comparison, and at that pre-war time) intelligentsia in the cities who were the main characters. But there are subtle, but despite that very strong image forming sentences. Bfisher mentioned the cockroach eggs, so, for example, Olanna's noticing of those in one short sentence gives an image of the rudimentary table, the hygiene problems, the presence of vermin, etc. in simple village life.
I have not worked in Africa nor even visited (was supposed to go there to do an assignment but, for me very happily, it fell through), but I have worked in a developing country, being an ex colony, with very a high crime rate and ethnic violence, some political instability and a similar privilege divide between subsistence village life and city living intelligentsia/government officials. I felt that the tone of the book carried its story in that type of environment very well.
Despite the non-serial nature of the book's four parts, which had me wondering, it all hung together for me. In the end I thought that structure allowed the book to progress its storyline without getting too cluttered along the way, but I have no idea as to what Adichie's own reasons were

.