From Sterwiki

The Galactic Empire Series contains Isaac Asimov's three earliest novels and one short story:

• The Stars, Like Dust (1951)
  
• The Currents of Space (1952)
  
• Pebble in the Sky (1950), his first novel
  
• 'Blind Alley' (1945), short story reprinted in The Early Asimov
  

They are only loosely connected. Their main common points are Asimov's idea of a future Galactic Empire, certain aspects of technology—hyperdrive, blaster pistols, 'neuronic whips'—and particular locations, such as the planet Trantor. Another connection was later established with Robots and Empire, where Asimov revealed how Earth became radioactive, as mentioned in The Stars, Like Dust and Pebble in the Sky. Some sources further this argument by asserting that The Stars, Like Dust takes place about one thousand years following the events of Robots and Empire.

Interestingly, the short story 'Blind Alley' is the only story set in the Foundation universe to feature non-human intelligence (not counting robots and Gaia).

Asimov later integrated them into his all-engulfing Foundation series. Some contortion was required to explain how the robots
of the Robot Series are almost completely absent from the Empire novels. In reality, this was because the magazine editor Asimov worked with at the time (John W. Campbell) disliked robots in science fiction, and discouraged Asimov from including them.

th: จักรวรรดิ (ชุดหนังสือ)