What are the most popular old science fiction books in the list of old science fiction books?

I'm not sure which ones are the most popular exactly, but 'Snow Crash' by Neal Stephenson is often highly regarded. It's set in a future where the world has been transformed by a new form of technology and virtual reality, and it has a really unique and engaging plot.

I'm not entirely sure which ones were the most popular, but 'Doomsday Book' was widely talked about. It had an interesting premise of time - traveling historians.

Another popular one could be 'The Uplift War'. It was part of a well - known series and had a lot of fans who were into the idea of the uplift concept, where lower species are 'uplifted' to sentience by higher ones. It had exciting battles and interesting alien species interactions.

Another popular one might be 'The Uplift War' by David Brin. It's part of a series and in 1989 it was attracting a lot of attention for its unique take on the evolution of intelligent species and the politics between them.

Sure. 'Frankenstein' by Mary Shelley is a great old science fiction book. It explores themes of creation and the consequences of playing God. Another one is 'The Time Machine' by H.G. Wells, which takes readers on a journey through time and makes us think about the future of humanity. Also, '20,000 Leagues Under the Sea' by Jules Verne is a classic, with its amazing descriptions of underwater adventures.

Another potentially popular one could be any book that dealt with emerging technologies at the time like genetic engineering. It would have caught the public's attention as it related to real - world scientific advancements. Books with such themes often create a sense of wonder and fear at the same time, making them very appealing to the science fiction reading audience.

One of the most popular was 'Hyperion'. It has a very unique narrative structure, which attracted a lot of readers. The world - building is also extremely detailed.

Among the popular ones is 'The Forever War'. It won several awards and has been highly regarded for its realistic take on the horrors of war in a science - fiction context. The way it deals with time differences due to space travel is also very interesting.

I think 'The Collapsing Empire' was quite popular. It got a lot of attention for its unique story and engaging characters.

Probably 'Snow Crash' is also popular. It was quite ahead of its time with its ideas about virtual worlds and the future of society. It combines cyberpunk elements with a really engaging story, which made it a hit among science fiction readers in 1999 and still remains popular today. The unique language and the fast - paced plot make it stand out in the list of 1999 science fiction books.