Venus was the first planet visited by Earth probes, beginning with the Mariner 2 probe in 1962 from the USA, followed by the Soviet Venera Program. The Venera program yielded the first color photos of Venus's surface, but the program ended in 1984. Since then, the only probe sent to Venus was the Magellan 2 probe in 1994, which imaged 98% of Venus's surface, and was crashed in order to get information on the atmosphere of the planet.
Why has so little been done by space programs to gather information on Venus, while Mars gets all the attention? Is it because Venus's atmoshpere makes it difficult to create probes that would survive there? Any suggested readings would be greatly appreciated, as I have not been able to find very extensive information online.
One thing you need to understand is that technological advancement isn't linear. It's due to need or desire. I know that might seem unrelated but I'll get back to it.
Similarly things arent done, projects aren't started unless there's a drive or a reason to due so.
Due to the volatile nature of Venus we won't be colonizing it anytime soon. Mars though, Mars is far less volatile. The reason why we put so much emphasis on reaching Mars rather than Venus is that it would be easier to both land on, and hopefully colonize Mars rather than Venus.
When asking yourself questions like this, and when your just studying history, always keep in mind how big of a factor reason is. We landed on the moon not because we were bound to do so, but because competition with Russia compelled us to do so. I have no doubt that if we were still in a cold war with Russia our space faring technology would be leagues ahead of where it is.
Now I can't go into detail about the topic, or recommend sources because I'm not well schooled on this topic. I just thought this answer would give some insight