Hornstrandir is freakin' amazing!
I went with no prior trekking experience and was totally fine! Isolated and empty, you won't see many people, especially if you are multi-day trekking, that also means you have to be prepared. I did a lot of research ahead of time, but found the reviews really lacking, so, here's the 411!
Wilderness Hiking: We lost the trail more times that I can count, crossed streams and rivers more times then I can count, and navigated extremely rugged terrain. To pass from fjord to fjord, there is also a good amount of climbing involved, about 1,500 meters at the top. Everyday you'll be going up and down, and not on nice trails. I had low top hiking shoes, HUGE mistake. I was told by a very experienced hiker that those boots were great and 80% of the people on the Appalachian Trail and PCT were sporting them. On day two, I was a broken man. My ankles were screaming, and I still had three more days left. They also turned out not to be water proof, despite saying so. That made the wetlands, streams, and snow caps not fun at all. Despite this major inconvenience, the views were ridiculous and well worth the pain. Some days, the only people we saw were at camp. Trekking poles are most necessary. They are very useful on snow caps and keeping your balance as you cross streams, of which there are many. We only had to wade across at two points, the rest of the flowing water can be creatively crossed in someway or another without getting wet. Everything is also much farther than it appears. Keep that in mind.
Getting There: Schedule a boat ahead of time. There are limited options for getting there from ísafjörður, so book ASAP. We took Sjóferðir, via West Tours. You can also book a tour with them or just a boat ride, either for a day hike, or a multi-day trek.
Food & Water & Outhouses: Fresh water is EVERYWHERE. We drank strait from streams. It's all snow melt, always moving, and with hundreds of small streams. With no glaciers, you also don't have to worry about silt. We drank the water untreated as did the others we shared camp with. Pack in your food, pack out your rubbish—pretty standard. Outhouses are at the campsites, but at those locations. You also don't need to worry about bears getting at your stuff. Polar bears are not native to Iceland. They do wash ashore occasionally, but are promptly shot upon their arrival.
Weather: *MUST READ* Listen up, because this is a big one. Weather can change incredibly fast, so be prepared for it. Fog can roll in at anytime and when it does your visibility is shot. When, not if, when you lose the trail, you need to be confident with a map and compass to make sure you don't disappear. I can't tell you how many times we were on the "trail", then, suddenly, walked into the trail, and that was without fog. You need to have a solid idea of your heading without a path to guide you and a clear view of your surroundings. That said, I was on Youtube looking up how to use a compass right before I left, yikes; therefore, you don't need to be an expert to survive. And most of all, it is wet. In the middle of July there was fog, wind, warm, cold, sunshine, snow, slush, wet ground, and water everywhere. Temperatures were 7-15 degrees Celsius. And because I want to end on a positive note, if you do get direct sun, it is absolute beautiful trekking weather! Once again, we went in the middle of July.
Wildlife: No predators to worry about. Birds and arctic foxes and bugs. The foxes are no bigger than cats, and the bugs, frankly, while really annoying, have zero interest in you. The Arctic has a serious mosquito problem, but not Iceland! It's an ecological anomaly. Hooray!
Heavy fog means you need a map and compass
All the Small things
Látravík: This is an inlet just south of the Horn. At the lighthouse you can get waffles, coffee, accommodations, a shower, a bathroom, and use of the kitchen.
Höfn: The biggest campsite, maybe 10 tents. It's located at Hornvík. There is a ranger station complete with a working toilet, faucet (cold water only), and a ranger. Also an outhouse.
Hesteryi: This is the main access point for day trippers. A collection of 5 or six buildings, here you will find the Doctors House, and it is great! We ended out trek here got great pancakes, coffee, and milk! There are also accommodations here as well as toilets. Because it is the main access point, there are a good amount of people here on a scheduled boat day. Just FYI, there are a ton of bugs, not interested in you, but do they get pretty annoying. There is also an elf palace on a nearby hill!