From the back cover:
"ICE's comprehensive science fiction RPG, Space Master, has been reformatted into a single book. It still contains all of the components that made it critically acclaimed by players and industry figures alike. The material in this version is identical to that in the Boxed Second Edition."
From the inside, about the revision:
"The Second Edition of Space Master updates the original role playing rules which first appeared in 1985, and integrates material from the original Space Master Companion (1986). Essentially, the SM system remains the same, and since it is based on the concepts of Rolemaster, it can easily be integrated with that fantasy system. Together, they set the stage for coherent science-fantasy and multi-genre campaigns."