Presented as a set of three softback rulebooks in a starter boxset, the 2nd edition was never published as a single separate standalone book like its predecessor or indeed any of it's successors (minus 7th Edition, but that's a bit different). The rulebooks were only available in 
The Boxed Game, along with 
Battle For Armageddon Scenarios campaign booklet and 
Codex Army Lists booklet for the included miniatures.
It differed to 
Warhammer 40,000: Rogue Trader in many ways, but foremost the separation into logical rulebooks and 
The Codexes (game play, weapons and inidividual books for each faction), with the Codex Imperialis being a stop-gap solution until 
The Codexes were released.