Introduction to Borderlands saga

Borderlands 1 can be a bit bland to play solo, but all others are well done for soloplayers - no worries.
It's also not really a difficult FPS.
It rather requires good equipment than good "aim" - so it's pretty casual :)

Series is easy enough to solo. And I had fun soloing it. Think of it as a single player action FPS with a few RPG (OTHER than the launchers) elements in it. I beat all 3 solo, although TPS was a little challenging at my level.

I started with Borderlands 2, and logged in a couple hundred hours before I got bored. didn't even realize it was co-op until much later.
I've barely started Borderlands 1. seems pretty similar, but, still a little FPS'ed out for now.

Coming from someone who's solo-ed all 3, Borderlands 1 may be a bit boring to play alone but the other two are great fun. They're also not very hard.

I really enjoy the Borderlands series - but I'm an old person who played too much Doom (the original Doom) and I just like running around like a madman and shooting barrels when things are standing next to them. If you want a hardcore tactical shooter where you need to use cover and remember which key is crouch then you may be disappointed. If you fancy a more casual FPS then this might well be great.

The first game isn't the best and if you don't enjoy the humour or the art style (quite possible) then you won't enjoy it and will find it especially boring in single-player mode. Borderlands 2 had a lot more to do and a lot of other improvements - some people still hated the jokes and the art, but certainly there is better balancing and enough content that I think most people would still find it enjoyable even in single-player. The Pre-Sequel wasn't as good as Borderlands 2 for various reasons but could still make a good single-player experience.

Thanks to everybody for the comments! Maybe I'll wait until finish another games that I'm playing actually. Greetings!

borderlands can be played alone, but don't expect to fight the "raid boss" in the first one, or the ones in borderlands 2.
games are easy unless you change the difficulty, obviously (you need to beat the game and restart).