I could find no decent screenshots, so here's a Let's Play video @norgg found for me.
You start out piloting a small unarmed shuttlecraft in orbit around a neutral planet. From there, you can work your way up to better ships, better equipment, and increasing fame or infamy. The known galaxy is largely divided into the Confederation of the core worlds and the Rebellion of the fringe, with a fair number of neutral planets and stations scattered between. There is constant low-level warfare between these two factions, and increasing numbers of pirates as you head towards the fringe. You can eventually join one of the factions as a mercenary, or just stay independent as a pirate or vigilante.
What made the game exceptional for the time was its extreme moddability. Virtually nothing in the game world was hardcoded. Everything was data-driven by Macintosh resources, a now mostly forgotten system for storing structured binary data. The game could be supplied with mods ("plugins") of additional resource files to be loaded in. As a result, adding a new solar system was as simple as creating a few planet records and a system record and wiring them in with hyperspace connections. Even complex entities like new ships and missions were pretty easy to add.
For many years, there was a very active modding community around the game, adding new content or doing "total conversions" that swapped out the entire game world with a new one. From these mods there arose two sequels, Escape Velocity: Override, and Escape Velocity: Nova. The former was basically an officially sanctified total conversion, whereas the latter started out as a conversion effort but eventually included a major engine upgrade.
Nova was released in 2002 and after that, things sadly... stopped. No further iterations of the game ever occurred. Ambrosia Software, the games' publisher, hinted that EV Nova had been a commercial failure, its modest success in sales not offsetting the vast costs of the major engine upgrade. The Escape Velocity series was originally produced for Macintosh, and while the final game also had a Windows version, it was not "at home" there, and probably never really benefited from the much bigger Windows market.
Ambrosia shifted its focus to utility programs and less ambitious games, and appears to have ceased releasing anything new about a year ago. The games market changed repeatedly: Escape Velocity was an Indie game hit long before the modern Indie world came into being. I've poked Ambrosia Software about getting EV: Nova onto Steam or GOG.com, as it seems to me that the game could do quite well with a new audience, but have heard nothing back.
There are of course plenty of newer games where you fly through space and do missions - EV was clearly inspired by Elite, and Elite: Dangerous has just come out, and EVE Online is going strong. One could theorize about an alternate timeline where Ambrosia took a risk, ended up lucky, and tens of thousands of people are now playing EV: Online. That didn't happen, so the question is whether there's anything worth salvaging from this line of games that isn't pure nostalgia. (Yes, you can play EV: Nova. There's a demo, and the full game costs a whopping $30. Prices from the past.)
On the face of it, EV is just a less technically interesting Elite, replacing 3D combat and navigation with 2D. That in itself would suit some people who aren't fond of 3D space combat as a genre. And indeed, there is a pretty close successor game to EV, probably unintentionally: Sunless Sea. You're on a ship rather than a spaceship, but the missions, trading, and 2D navigation are not entirely unlike EV. Sunless Sea is pretty fun, and doing pretty well for itself, so the same thing in space could do well too.
And that's missing out on EV's killer feature: trivial modding. Avoid the temptation of overly fancy graphics or new, complex game mechanics, and the game world remains utterly simple to represent: a list of places, things and missions with some cross-links. EV never had a proper editor, but it wouldn't be difficult to build one. There are no recursive relationships between entities, there is no scripting beyond mission definitions and effects, and everything can be represented by text, numbers, and links to other entities.
It's... tempting. I feel that I could remake the original Escape Velocity within a week, excepting missions. I know the game well enough to simply build it out of the obvious required parts, and the vast increase in processing power since 1996 means that I'd have to spend zero effort on optimization. (Unlike the original, which was a terrifying thing of C and handwritten 68k assembly needed to blit the graphics to the screen fast enough.) Beyond that, some planning and work would yield a mission system of comparable power to the original, and a simple GUI editor for all the game data. Create a decent default game world (original EV was nice but frankly very sparse in its missions), put the whole thing on itch.io for an optional fiver, and encourage people to mod to their heart's content.
Ambrosia SW have since responded to me, stating on the topic of EV: Nova on Steam: "We considered it a couple years ago and decided it wasn't for us. Who knows, that may change down the road?" Very glad to see that they're still around and just less active.