I do not think that any detective, sci-fi or adventure was a deficit. But good books were indeed. But as I already said this was because all books were so cheap that people bought very many books. By 1990s I had 5 bookcases (2 of which were cupboards actually) filled with books each shelf in two rows, plus 16 separate wall shelves, plus the space under a divan plus entresol above the entrance plus a heap in the closet box.
Yes. What the people needed was decided by the Gosplan as anything that was produced. They had plans how many detectives the people need, how many adventures and so on. This was calculated "scientifically" based on people's free time etc. But they did not account that many people just bought more books than they could even theoretically read (many wanted to look "learned" by having a large library and many wanted to pass the books to their children etc).