Stars Without Number: Revised Edition is the best kind of "2nd edition" that other RPG titles should aspire to emulate. Why? Because it did not throw away the baby with the bathwater. It is fully compatible with all the original SWN sourcebooks and adventures. The original Stars Without Number was an amazing but identifiably "indie" set of rules. Was it bad? No, it was great, chock full of great ideas, interesting systems of rules, exciting content. But as a gamer who has been around since the '77 basic set, I've certainly read my fair share of RPG rule books, and the original SWN was a very well done "budget" book that looked very good but was not the highest quality layouts and artwork I'd seen before. This new Revised Edition corrects all of that, in spades, and adds a ton of new excellent content as well. There were a few issues I had with the earlier system, and almost all of those minor issues I had have been corrected with the Revised Edition also.
This game starts with the basic OSR d20 core system of abilities we've all come to know and love (or at least understand), as a base, and then builds onto it custom layers of science fiction content onto it. So, no, you do not have "Fighter" but you have a warrior class that is similar to Fighter and you have an Expert class similar to Thief (but a far better way to handle the skills compared to 1e), and you have a Psychic to be the "magic user" to add some cool psychic powers to the game. And that's just for starters, there's tons of customization that can go into individual classes, and for the most part, you can develop the character in whatever directions you choose.
There's also some amazingly great GM tools included in this book that can be useful for anyone playing any type of science fiction space opera type setting regardless of the rules you're using. There's chapters on designing your own space sectors, with advise on handling interstellar trade, societies, diplomacy, alien physiology and psychology, robots and VI's (androids or droids with "virtual intelligence" or semi-sentience),how to develop alien, robot, or VI player character classes, factions, etc. Starfinder GM's may want to consider getting this just for its world-building and sandbox play assistance.
But is there anything negative to say about SWN:RE? For fans of lighter "indie" roleplaying games similar to Apocalypse World, Stars Without Number Revised Edition like it's original will feel a bit "heavy" in terms of game mechanics. There's a lot of little mechanics to either remember or reference in the book when they come into play. Not everything is handled by one simple 2d6 mechanic, although basic skill use is, so that's something that fans of PbtA games will probably appreciate. But for the most part, you will need amost all of your polyhedrals to play SWN:RE, and you'll want the handy GM's screen set up while playing so you can quickly reference various charts and tables that will be required to successfully judicate the mostly player-driven narrative. Since SWN is intended to be a player-driven sandbox style game, it has similarities with "indie" titles following the AWE / PbtA model, but there are more rules to handle all of the various situations that can come up in a science fiction setting. For example, starship design, starship combat, designing robotics and VI's and True AI's, hacking into stuff, psychic abilities, the effects of scifi hazards like vacuum, radiation, pressure sickness, poisons, disease (terran and alien), technology levels, etc. All of that may seem overwhelming for a PbtA GM, but you know what? It's there if you want to use it, and if not, you can chunk that and just let the narrative dictate the result just like always because it's YOUR GAME and as the GM you're the final arbiter of the results of any attempted action on the part of the player or non-player characters.
Revised Edition is FULLY COMPATIBLE with the supplements and adventures of the original edition of the rules, so you don't have to go re-buy all of your SWN books to stay current. Or if you are new to SWN, you already have available a lot of adventures and supplements compaitible with this new rulebook! And did I mention that the production values are way up? WAY UP, amazingly beautiful full page artworks and a full color printing that just pops right off the page and is absolutely gorgeous. Along with all the new optional content like Transhuman campaigns, AI's, Mecha, and even Space Magic, SWN Revised is an incredible value for the price and a gorgeous edition to any scifi fan's bookshelf.
I did participate in this book's Kickstarter, full disclosure, but I bought this book, and this is not a paid review. I honestly feel this is one of the best science fiction RPG rulebooks ever produced.