I think this one is a pretty safe recommendation. I found it on a list of protocyberpunk stories a few years ago, and it looks like it shows up on similar lists fairly often, but I think it better qualifies just as early cyberpunk. It was published a month after Neuromancer, and Shiner thanks Gibson and Sterling for their help in the author’s note at the end. The setting, though distinct, feels very similar to the Sprawl books. It has not just the usual elements (a dying world with megacorporations ruling over the ruins of nations and governments as it all slowly collapses into disrepair and apathy, corporate soldiers and a chaotic war with ever-changing alliances where the killing was done more for boardroom dealings thousands of miles away, stolen wetware, heck even mirrored sunglasses, but it also has a lot of the same feel, the vivid descriptions, and a similar kind of dreamlike tone in places. I’d say Frontera somehow feels a little less steeped in the 1980s, and might be missing some stuff like AI, but if you like Gibson’s sprawl books, I think it’s about as close as you can get in terms of tone and feel.
So what’s it about? When things got bad and the governments collapsed, Earth abandoned the colonies on Mars. The corporation that ended up with NASA’s property on the ground and in orbit decides to finance a sketchy trip to mars using old equipment on a rushed timetable. Their reasons are kept secret even to most of the crew but even the back of the book will tell you the colonists are still alive out there, and they have something multiple corporations, including the ones who obtained the remnants of the soviet space program, want very badly.
Overall I quite like it, I think it fits nicely into the early days of cyberpunk, and it’s a fun story. I’m not super into the science of colonizing Mars, but I suspect some stuff has been figured out since the book was written. Still, it’s a great story, and I very much recommend it.