I have played this for 25 hours now, about 22 hours with friends and the rest alone. Playing solo is absolutely the worst way to engage with this game. Whereas the original Risk of Rain was a solid single-player experience, even today, Risk of Rain 2 simply isn't. Stringing together insane combos with your friends (Engineer turrets + Razor wire + Hellfire tincture + Bustling fungus + Mired urn – just drop a shield around your turrets and sit back and watch bosses die in 4-5 seconds) is fun, compounding the complexity of your 'setup' the more people you play with. The gunplay and abilities themselves are rarely that engaging and multiplayer is more often than not just a fight for loot between friends rather than a cooperative effort. None of your abilities are made for co-op. You can't help a friend out of a tricky situation with a support ability, you just have to throw yourself into the line of fire and hope the minions focus you. It's the sort of mindless fun that is great when you are around people you like playing video games with, but it falls apart completely when its gameplay mechanisms are judged on their own merits.

I will still continue to play this with friends – I love stealing their loot and blaming it on the boundless eagerness of my innate 'entrepreneurial spirit' and drop not-so-subtle references to Atlas Shrugged – but I can't imagine ever booting this up to play it solo again.