I just spent a week in Düsseldorf on holiday. I know it's not a "touristy" choice but I'm a big public transportation geek and there's a lot of interest in that line in the area. I went by train from London using one of the ultra-cheap deals you can get on bahn.de, changing at Brussels and Cologne. I really was not impressed with the German ICE train from Brussels. My reserved seat was against the direction of travel and against a pillar with little view out. To make things worse the air conditioning in the carriage didn't seem to be working well and I got seriously travel-sick for the first time in years. But the worst thing about the ICE even with a decent seat is that there are no luggage racks at the end of the carriages. Everything has to go above the seats and if you have heavy luggage it's very inconvenient. I stayed at the Max Hotel Garni in Düsseldorf which was recommended by a guide book. Very nice bed-and-breakfast, comfortable beds and rooms cleaned daily. You also get a free public transportation pass for the entire Rhine-Ruhr area for the duration of your stay, which was a huge advantage for me given the amount of travelling I was doing. The only problem was that there were no opaque curtains in the room and if I hadn't had a sleepmask I'd have been in trouble sleeping.
Part 2: The Ruhr is definitely worth visiting if you're into industrial archaeology. Several of the old coal mines and steelworks are now museums. However most labelling and tours are not in English so you need reasonable German. The exception is the Ruhr Museum in the old Zollverein coal mine near Essen, which does have English labelling and is very interesting, as well as being a spectacular building. I went to a number of art museums in the area, my favourites being the K20 in Düsseldorf and the Folkwang in Essen. The Ostwall museum in Dortmund is also very good but is more focussed on post-WWII material. The kunstpalais museum in Düsseldorf has a specialist collection of glassware that is hugely recommended if you're interested. One remarkable experience is the Schwebebahn railway in Wupperthal, an elevated monorail dated from the early 20th-century that is a real method of local transport rather than a fairground ride. Although it looks a bit scary the ride is actually very safe-seeming, and I'm quite scared of heights. It's just a bit of an odd feeling the first time the train body swings out on a bend.