Here is a book from the soviet era, about Venus
https://www.goodreads.com/book/show/23302599
"Тайна утренней зари"/"The Mystery of the Dawn"/"Taina Luceafărului".
As for their space program, I do believe they had almost similar investment for Venus and Mars, just Venus was more approachable and the missions were more fruitful(?). They canceled some Mars and Venus programs in time. Some wikipedia page about USSR space program: