The Hitchhiker’s Guide to the Galaxy by Douglas Adams
Optimistic Space Scifi
97 books — 103 voters

Old Man's War by John Scalzi
The Old Man's War Universe
18 books — 15 voters
Bomb by Steve Sheinkin
Manhattan Project
55 books — 23 voters

Godless by Dan   Barker
Notable Atheist Books
544 books — 938 voters
The Demon-Haunted World by Carl Sagan
A Skeptic's Library
170 books — 127 voters

Rendezvous with Rama by Arthur C. Clarke
SF Masterworks
196 books — 721 voters
The Time Traveler's Wife by Audrey Niffenegger
Best Time Travel Fiction
1,957 books — 5,244 voters

I, Robot by Isaac Asimov
Best Science Fiction
3,651 books — 6,975 voters
Ender’s Game by Orson Scott Card
Military Science Fiction
839 books — 1,134 voters

Cosmos by Carl Sagan
Best Science Books - Non-Fiction Only
1,837 books — 3,600 voters
1984 by George Orwell
Best Dystopian and Post-Apocalyptic Fiction
3,748 books — 25,990 voters