A friend asked me to read this, so we can discuss it. (It's a long story.) So far, I've made the following inferences:

-- Karl Popper was a humanist and and advocate for social justice, but he was anti-communist by the time he wrote this book.

-- Popper wants to discredit the philosophical foundation of Marxism, historical materialism, which is a branch of historicism. So, he wants to discredit historicism.

-- Popper believes that the origins of historicism lie with Plato. So, he feels he must thoroughly investigate Plato's version of historicism, and then discredit it, before he moves on to Hegel, Marx, etc. (I'm still mired in the long Plato discussion.)

Did I get that right, so far, more or less?

What I don't understand is why Popper found it necessary to review Plato so laboriously. It's really tedious to me. The only explanation that occurs to me is that Plato was held in higher regard in the late 1930s than he is today, and that Plato's version of historicism had not seriously been questioned before Popper came along, so Popper wanted to refute it thoroughly and convincingly. That's just a guess, though. I'm only a casual student of philosophy.

Beyond that, additional context, to help me make sense of this long and tedious book would be appreciated.