I don't know why they stuck that 'even for American readers' on the end. Popper was always a highly relevant book, for Americans, Brits, and anyone else concerned with the freedom of the individual as opposed to the demands of the almighty state.
First published in 1945, Popper's book is chiefly noteworthy, I suppose, for its intellectual demolition of Marxism. For ever after, it was difficuit -- well, actually impossible -- for any Marxist to claim, as they had hitherto, that Marxism was 'scientific'.
The Complete Review provides its own little introductory essay to Popper and his thinking. This essay is mercifully written in plain English -- and what a massive relief that is, when one contemplates the ghastly academic bullshit in which it might have been couched. Five stars to whoever wrote it.
The essay makes a number of very interesting points, one of them being that Marx's heart was in the right place. Given the times in which he lived, he was quite right to highlight the miserable condition of the working classes. And, I may add, it was really not surprising that he should take the view that revolution inevitable.
Here's the conclusion of the Complete Review's essay:
In a world where religious fundamentalism again manages to move the masses (and leads far too many to do the outrageous), and powerful democratic states like the United States move, under the jr. Bush administration, to limit the rights and voices of individuals, while arguing that they benevolently (yet untransparently) are working towards the greater good, The Open Society and its Enemies remains an essential work. And it's also an engaging and accessible read.
Well, the Complete Review essay is certainly recommended. Whether you feel strong enough to tackle Popper himself is up to you. I read him as a young man and was no doubt all the better for it.