as someone who has over the years been to every major and certain minor K-Kamps (as part of my "work assignments" as a writer), I can only add:

Go! No matter how and when. Just go.

>>Go! No matter how and when. Just go.<<

They likely did - The trip was 3+ months ago -- maybe umretdd topped it to advertise the tour company.

I'll be in Krakow mid October and contacted the hotel we'll be staying at if we should pre-book Auschwitz and they guaranteed we could do it on arrival (we are staying 5 nights, plan to do this on day 3). I'll talk to my traveling companion who still doesn't know where we're going, to see if she wants to book private or group transportation. Might use KrakowDirect too...

I was there in July. I booked through my hotel, but the same thing can be booked at one of several places around the main square. The prices are similar but if you shop around you can save a little bit. The drive there from the center of Krakow is one and a half to two hours and pretty boring. I don't think it would matter if you were on a large bus, mini van, or private car. Once you get there whoever drove you there hands you over to an official guide and you join their group. At least mid day in July that was the only option. It was very crowded, there is no option for any kind of solitude, it won't matter what kind of group you go with. Possibly by mid Oct it may be different but don't count on it.

On the other hand, the guides that Auschwitz provide are excellent. The one thing I liked about the company I used was they showed a 45 min video in the mini van on the way there which I think added to the experience. I know several of the companies did this. I doubt very much you won't be able to book the day before you want to go.

Tour groups are great for the reasons isabel gives but if you're the do-it-yourself type like moi it is easy also to take the train or public bus to Oscwiecz (or however the Polish town Auschwitz is in is spelt!) and then a local bus to either of the two camps - I walked from the train station first to Auschwitz and then from there to Birkenau - Birkenau to me was much more sobering than even Auschwitz - Birkenau was a killing camp and a work camp - Auschwitz mainly a work camp - do both for sure but do not slight either one.

I took the kind of trip isabel describes. It was the depths of winter, so not so crowded. The bus company guide was just on the wrong side of perky rather than customer-friendly (dishing out coloured labels for us to wear to distinguish the two different busloads, without a hint of irony), but the camp guide was excellent. I don't know how they do it, day in and day out.