The blurb on the front cover of the paperback version reads "A panoramic story of what happens to a world gone super intelligent!". That sums the basic premise up so perfectly it is worth repeating.
I love high concepts, they save me from struggling to write an accurate synopsis. Brain Wave is about every living creature in the world suddenly having their intellect more than quadrupled. Such a deceptively simple premise, it seems like anybody can write a story about this. However, Poul Anderson is one of sf's all time greats, and here he managed to spin out a lot of imaginative yet entirely believable ramifications from such an event.
Referring back to that aforementioned blurb again the "panoramic story" part refers to a multiple viewpoints structure which allows the author to create a detailed post-IQ boost world. Here Anderson focuses on a wide range of people, among them some scientists, a house wife, a simple farmhand, and some monkeys. Super intellect - as it turns out - is not desirable for everyone, a lot of people go insane from suddenly thinking and perceiving too much. People who holds menial jobs now find repetition and lack of challenge intolerable so they quit in droves. While this is not a post apocalypse world it does have a similar feel to it, with government breaking down, people deserting their jobs, and pigs attacking people!
This is a very short novel (175 pages) so not a lot of time is spent on character development, I do like the farmhand plot strand though, it has a Flowers for Algernon vibe to it (without the tragic ending). The average housewife's story is also poignant. Andersen's prose is as highly readable as ever, his science background is once again put to good use. I like his explanation (not infodump) of how this Brain Wave came about, for Tau Zero fans (often cited as Anderson's best book) there is a little subplot that does something different with the runaway spaceship idea.
This is an excellent little book, well worth anybody's time. It may not actually boost your intelligence but may give it a wee nudge in the right direction!