Hayek on interest rates

What book (and maybe chapter) do i need to read to understand Hayek’s theory on interest rates?
And is the theory still valid according to modern austrian economists?

I think 2 good books of his worth reading are Prices and Production (1931) and The Pure Theory of Capital (1941). I don’t know if he was actually a proponent of the time preference theory of interest which most Austrians generall agree with and accept. (There has been development on the theory of interest since, and not all austrian scholars adopt the time-preference theory exactly.)

If you want to delve into the theories of interest and do a bit of a heavier study, I think a good place to start would be Capital and Interest:

http://mises.org/resources/164

Someone else around here probably could make a better suggestion/more suggestions as to how to go about learning this stuff.