I attended the N24 this year and can add some more "what it's like" impressions.
We flew into Frankfurt on the Thursday and rented a VW camper van. It's a 2-hour drive from Frankfurt to the 'Ring.
Camping is first-come first-served, and administered separately from event tickets. If you want to camp trackside on the Nordschleife you've gotta show up way earlier than Thursday. Seemed like most of the people camped there had been around all week. There's a number of camping areas at the south end of the track and we got turned away from 5 or 6 full areas before finally gaining access to a field about halfway to the village of Mullenbach. We had been worried, but there's lots of room.
We had ambitions of filling up our van's water reservoir and getting groceries en route from Frankfurt, but we had not accounted for it being Ascension Day (May 18) and we couldn't find an open grocery store. We survived Thursday night living off gas station snacks and beer, and on Friday morning resolved to leave the campsite & acquire supplies. There's a Lidl in Kelberg about 6km south of the GP track . Coming & going from the campground is no issue once you've secured your site, but getting a VW camper on eco tires out of a damp field is an issue and we got it pretty decently stuck. Had to negotiate a tow from some logistics guys with a tractor.
Some of the busier campgrounds had people blasting music at deafening volumes late into the night. We were lucky to be in a calmer area. I'm not sure how you would plan around this or if there are designated quiet areas.
We didn't have a set plan for watching the supporting events, we just wandered around and soaked up the atmosphere. Great car-spotting, lots of interesting pavilions and food/merch stands. The 3h Classic is a treat. There was also a Touring Legends event with vintage DTM and Group A cars. Paddock access, even during the main event, is similar to IMSA events - you can wander around the backside of the pits and watch the teams at work in their garages and mill about all the race transporters and HQ tents.
On the big day we loaded up our backpacks with beer and snacks then headed out along the Nordschleife, going clockwise starting from the GP track. It is at this point I should specify that there are two theories of how to enjoy the N24: you can (A) find a good spot, settle in and enjoy the race, maybe relocating every so often, or (B) try to cover as much ground as possible, which is to say, hike as many of the 'Ring's 20km length as you can. I was on Team A, but my friends were on Team B. I soon came to regret not having packed hiking boots and a more substantial backpack, so if you're going to do this I recommend reaching consensus on a strategy ahead of time.
I cannot exaggerate how huge the Nordschleife is. There were moments in our day, between viewing spots, where we could not see any of the circuit, only fields and forests and hills for as far as the eye could see, and realize that somehow a racetrack encloses all this. The elevation change, too, is hard to appeciate from pictures or videos or racing games. It's pretty dramatic.
We befriended a few German superfans in the lead-up to the race and they took us under their wing. Given the scope of the event, insider intel is extremely valuable. We watched the race start from a vantage point on the fast downhill section leading to Fuchsroehre, then spent the rest of the afternoon hiking along the west side of the track to the town of Adenau, which the track actually passes over. We had dinner on a patio there and stocked up on beer & trail mix at the grocery store, then split up with our German pals as my bad knee was starting to slow me down.
The sections of the track from Adenau to the Karussell are apparently tough going and not great for viewing, so we hired a cab and skipped ahead. We marked midnight standing with the crowd on the inside of the Karussell watching cars drop hard into the banked concrete & their headlights circling around us in the dark. Mesmerizing.
The stretch from Karussell to about Bruennchen (aka. "Youtube Corner") is apparently called the party mile. Huge elaborate soundstages, techno music at deafening volumes, lightshows, smoke machines, fireworks. Apparently drivers have complained that this chaos can be distracting, but to an extent the excess seems to be viewed as part of the N24's unique culture. Because it's near a main road and easy to service, there are food and drink stalls next to the track at this location. Here at 4am we had some currywursts mit pomme and then caught a shuttle bus back to get a few hours sleep and see the ending of the race along the GP track.
Anyhow - sorry for the novella - if you're into sports car racing at all, I highly recommend going. It's an unforgettable experience.
