| Author | Isaac Asimov |
| Copyright Holder | Isaac Asimov |
| Series | Galactic Empire |
| Publisher Series | Sphere Science Fiction |
| Publisher | Sphere, Sphere Books, Sphere Books Limited |
| First Published by | Sidgwick & Jackson |
| Printed by | Hazell, Watson & Viney Ltd |
| Format | Paperback |
| Language | English |
| Location | UK |
| Copyright | 1958 |
| This Edition Published | 1969 |
| Pages / Font | 186 pages / Linotype Times |
| ISBN | 0 7221 1241 6 |
| Price | 5/0 United Kingdom |
| Price | 80c Australia |
| Price | 75c New Zealand |
| Price | 60c South Africs |
| Price | 6/00 East Africa |