To those gamers only impressed by graphics and presentation I suggest that you look away now because the Mount and Blade series, whilst providing a great deal of action-RPG entertainment in an Elder Scrolls-Lite sort of way, looks like a game that fell out of the Ugly Tree and hit most of the branches on the the way down. It's buggy, there's no real story to suck you in and it looks like the back end of a donkey that fell through a hedge and into a trash compactor...but it's also really quite a lot of fun thanks to a world full of economic opportunity and political romance, a deep combat system and a genuine 'free-for-all' spirit.
Steam are currently offering the original for £6.25 at the moment, but that's an awful price considering you can get it from Amazon for just under a fiver. However, if you just want to leap into the action with Warband, which is a stand-alone sequel, £8.50 happens to be around five quid cheaper than anywhere else.
The two games suffer from similar issues, and share the same positives. Both are relatively solid open world medieval RPGs with surprisingly deep gameplay mechanics. The combat is especially noteworthy here, with timing, direction angle, positioning, weapon and, of course, you're own stats determining how effective your strikes are, as is the rich, but steep, learning curve when facing the economic aspects of the open world of Calradia. Calradia's citizens might be information spewing automatons rather than finely represented human beings, but the world itself is a treasure trove that's stuffed with things to do.
I'd plump for the expansion if I were you, to be honest. It looks better, plays better (there aren't so many bugs, although there are still a few that will have you either howling with laughter or weeping with despair) and there's even a multiplayer component in there too. Plus, , there's now the ability to found your own kingdom and then rule it with an iron fist...or not, if you prefer, and now longer will you have to charge around everywhere picking up your tithes. It automatically gets deposited into your account. It would have been nice to have co-op on the full map, but sadly you can't have everything. Not for £8.50 anyway.