I just came across this great website exploring the history of science fiction books from Penguin. It as a nicely interactive front page where you can click on a cover and read a short description of the
From the website:
Penguin Books was founded by Allen Lane in 1935 as a paperback imprint of The Bodley Head publishing house. The new venture was an immediate success and early the following year Penguin was established as a company in its own right. An important factor in this success was the books’ eye-catching cover design which featured two horizontal bands of colour – orange for fiction, green for crime, blue for biography – separated by a third, white band containing the title and author’s name. These simple yet striking covers gave the books a refreshing, modern look and remained in use for many years, acquiring iconic status along the way as examples of classic twentieth-century design.
There’s also a great table of contents page linking to short articles describing each “movement” and giving examples from the covers.