X-plorers is somewhere in the middle of Starships & Spacemen and White Star. Both thematically and in terms of rules. There is a more of an old school vibe of this one. So to continue my analogies to the point of breaking, X-plorers is more Buck Rogers, the old serials and 50s sci-fi movies.
The book itself is 41 pages. This includes cover, title page, ogl page and a trademark license. The trademark license is nice. You can make content that is "X-Plorers Compatible" as long as you abide by the license. Yes other games do this too.
Characters have class, hit points, and levels just like most OSR books. The characters in X-Plorers though only have 4 attributes; Agility, Intelligence, Physique and Presence. They are still ranked 3-18. There are also four classes; Scientist, Soldier, Scouts and Technicians. Personally I think some sort of Royalty or Ambassador class might have been a nice inclusion as well.
There are some multi-classing rules too which are nice to see.
Equipment is covered next. The basic unit of commerce is the credit (cr). It functions largely the same way the gold piece does. Gear and weapons are covered, but also vehicles and robots. Near the end we cover skills as well.
Chapter 3 covers running the game. This includes saves, combat and skill checks. All similar territory to other games.
Chapter 4 details Space. This covers ships, buying and outfitting with crew as well as combat. Each phase of combat is discussed, so the gunner, engineer, pilot and so on. This reminds me of some the of old school Naval ship battles. Ship repair is also covered.
This is followed by a referee's section. This covers creating a game and running one. There is a small section on Aliens and Planets.
NPCs, Allies and Monsters are featured in the next section. I would have liked more, but again, these are easy to take from any fantasy game.
Chapter X is an adventure/background piece on Roswell. There are even stats for the Greys, whic is really cool to be honest.
Chapter Y covers psionics and pyschic characters. This is also pretty cool.
We end with some sheets for characters and ships.
X-plorers is a light game and designed to emulate the games of the 70s. So in that respect it does the job well. Some people will want more, but there is still a lot here. Rule-wise it reminds me more of White Box Swords & Wizardry, in fact you could use S&W as the rules and the rest as add-on.
This is the same as the full featured version, only no art.