The Internet Archive, despite its usefulness, seems to be an under-used resource. For the curious or sneaky, its Wayback Machine is a handy tool for finding past versions of defunct or revised websites. But there's also a large collection of open source material, including out-of-copyright texts (which I've cited here before) and even feature films.
Alexander Korda's Things to Come is one example. I admit I've never particularly liked it - the screenplay, written by HG Wells himself, is very preachy and stylised - but visually it's remarkable for its time. The source book, The Shape of Things to Come, is also online: not a novel but an imaginary historical account from the early 1900s to 2100. It's presented through the device of a diplomat using the then-fashionable techniques of JW Dunne - see An Experiment with Time - dreaming a history book written in 2106.
The Shape of Things to Come is well worth reading, in parts (I personally find Well's idealistic final section about world recovery through a rational world state tedious and unlikely). But it's remarkable astute in its prediction for the 1930s; Wells was very nearly right in his date for the onset of WW2, and completely right in recognition of the importance of aerial warfare and the submarine missile deterrent.
He is, however, very influenced by World War 1. His WW2 starts with a similar pivotal killing to that of Archduke Ferdinand: in this case a young Nazi shoots a Jewish rail passenger on the mistaken assumption that the latter is making faces at him (he is really struggling with stuck false teeth). Wells imagines gas warfare, important in WW1, as the most destructive aspect of WW2 (something that, partly through the Geneva Protocol and partly through fortunate circumstance 1, didn't happen in reality).
Wells' WW2 continues until 1949, followed by a pandemic fever (akin to the post-WW1 influenza pandemic) peaking in the mid-1950s. The resultant Balkanized Europe and an America caught up in ritualistic denial of its collapse, described in the Europe in 1960 and America in Liquidation chapters, are a very dark and modern post-apocalyptic vision, unlike the somewhat idyllic post-civilisation England envisaged by the Victorian pastoralist Richard Jefferies in After London.
The Germans had G-series nerve agents, but didn't use them on the mistaken assumption that the Allies also did.