The author's bio note at the end of The Warlock of Firetop Mountain made mention of the "big three" roleplaying games of the time: Dungeons & Dragons, RuneQuest, and Traveller. With Stellar Adventures (Graham Bottley and Jonathan Hicks), the Advanced Fighting Fantasy (AFF) Second Edition rules makes the jump into science fiction, and just as AFF makes as good, or better, a fantasy game as D&D and RuneQuest, Stellar Adventures is an excellent, fast, flexible system in the mode of Traveller and other sci-fi systems.
Character generation is, if anything, slightly faster than in AFF. SKILL, STAMINA, LUCK, and PSI (the equivalent of magic) and TECH (the technology/engineering rating for android characters) are allocated from a pool of points. Then, the player selects special skills and skill levels from a list and a distinguishing Talent.
The rules of the game are the same as those for AFF, and very clearly explained. The small table on difficulty modifiers is a masterpiece of concise design. The basic system from AFF is simple and robust, it's just unfortunate that the "Roll over SKILL" option repeats an error from the original AFF book. The target number for a roll-over system for Skill tests should be 14, not 15, to duplicate the probabilities of the roll-under system.
Combat, of course, is a large section of the rules, and it's here that Stellar Adventures takes a subtle but radical step. In AFF, combat is resolved by opposed rolls, and this makes perfect sense because most combat is hand-to-hand, a series of sword blows, claw swipes, and so on. Stellar Adventures retains the opposed roll mechanic – but the majority of combats are firefights, with ranged weapons. To a Traveller player, this is strange indeed. Surely aiming and firing a weapon is a test of Skill rather than an opposed test? But, on reflection, Stellar Adventures really makes this work. The opposed attack total isn't about taking a single shot; it's an abstraction of dodging, taking cover, finding the nerve to aim and shoot accurately in a chaotic exchange of fire. It makes sense that the more skilled combatant gets the first hit out of all this action, and a single combat roll handles this. The opposed combat roll still introduces some oddities, however, and in particular there's no penalty to hit when attacking out of a weapon's range (the penalty applies to damage instead). Personally, I would apply a range penalty to attack totals, giving the edge to longer-ranged weapons, and stipulate that a ranged attack must total at least 14 to hit, so that it's possible to roll the higher attack total and yet miss due to lack of accuracy.
As befits a multi-genre sci-fi rulebook, there are sections on equipment (including cybergear), robots (with a player character option), vehicles, and starships. The sections for vehicle and starship design are remarkable for their scope and simplicity. Unlike more convoluted system (High Guard for Traveller for instance), one just selects basic vehicle options like size and speed, adds weapons and armor, and then options in the form of modules, and then calculates the total cost of all features. This is a fast system that allows you to design almost any kind of vehicle or starship. Of course, the GM will have to keep a close eye on the armaments and enhancements, lest the PCs quickly assemble an unbeatable vessel, but the system provides the ability to build anything appropriate to the setting, from a motorbike to an Imperial Titan to a free trader to the Liberator. And there's a somewhat free-form vehicle combat system that follows the same conventions as personal combat, making it easily scaled and interesting for all players.
Setting design is handled in a similarly descriptive fashion, with "place characteristics" such as Size, Tech, and Society given a 2-12 score (either by rolling or assigning directly), with the GM interpreting these scores depending on the context. There's also a dice-drop method for determining star maps and solar systems, which has a nice element of random inspiration.
Reading Stellar Adventures, the Classic Traveller system often sprang to mind, as Stellar Adventures shares many general ideas with Traveller. Indeed, Stellar Adventures would model Traveller's sprawling stellar empire, mercenary companies, meandering tramp traders, and morally dubious sci-fi adventure well. But with a little GM adjustment, I think Stellar Adventures could scale up to space-opera, and even grimdark science-fantasy, or down to hard sci-fi, and the nice part is that the rules permit, even encourage, this. The only genre it's less likely to accommodate is broadly speculative transhumanism, and since there are no rules for hacking, cyberpunk would be a stretch (though doable). Stellar Adventures isn't perfect – no game is – and there's certainly something in here that I would tweak or tinker with, but Bottley and Hicks have adapted the AFF framework with great success to provide an easy, highly adjustable system for science fiction gaming.
[This review is based on a reading of the PDF rulebook, and not actual play.]