This is a reprint of the 1982 classic, "The Traveller Book" by Marc Miller. It had been years since I read it, but there are a lot of reasons this is a real classic.
The introductory material is very strong. It lays out a clear picture of what the referee and players are to do. It paints a picture of player-driven campaigns and a responsive GM whose most important role is to listen to the players and aim the campaign events at their interests.
The next section is on character creation, and details the famously interesting Traveller lifepath system (including "rolling for survival" in dangerous lifepath steps). This system has been praised by so many before me that anything I say about it is probably superfluous. It really is evocative and fun to see how your character's experiences help them develop. It provokes the imagination. It makes you want to make another character right away. It is clearly explained, laid out and easy to use. It is everything a background generation system should be. The section concludes with an example and, much overlooked in many games, a section on how to fill out the character sheet. This is something many games overlook, but which has survived in White Wolf and Wizards of the Coast products for good reason - the character sheet is your physical artifact of the character generation process and is really your chief connection to the process when you're actually playing the game.
Next is the combat system, with highly detailed weapons lists and ranges. A combat procedure checklist is included. After combat comes a space travel and economics system, which is highly mathematical and detailed. (Yes, a square root is involved for the calculation of travel times.)
A ship design system is next, which is highly tied in with the amount of debt the characters start in. The hilariously anachronistic computer system is still interesting to see what we thought computers of the far future would be like in 1982.
Other systems included are: space combat, alien animals, encounter creation (including patrons and rumors), and psionics. There's a fully developed set of adventure hooks set in a subsector of space, and two fully developed adventures based around exploring a strange pyramid and getting an exit visa. Both are interesting and exciting.
There's a brief overview of the setting of Traveller (though you may correctly surmise from the above that the game is meant to be highly customized for different groups). One interesting thing Traveller does is that instead of having players ask "what's in the ship's computer about this", there's actually a Library printout of what's in the ship's computer, and they can just leaf through and find it "in character".
This book contains everything you need to play one of the greatest science fiction RPGs of all time.
This presentation is just a scan of the 1982 book, with no copy/paste capability. Although there are bookmarks, for some reason they're just each of the pages' graphic file name. The table of contents, though of course non-hyperlinked, is very effective. Because of the crudeness of the presentation, I'm reviewer tilting down one star, but the sheer breadth of the material presented here along with its well-deserved place in the hobby means that I'm giving it very high marks and recommending it to everyone.