This question is specifically for Korean learners on this website. I was wondering how many Korean Words you had recorded on lingq before you were able to somewhat comfortably read children’s books on the level of, say, Harry Potter.
Just to clarify, Harry Potter, though it’s written for a younger audience, is not really a “children’s book” from the standpoint of readability. I think the official readability rating for the first Harry Potter book is around the same level as other beach blanket bestsellers such as DaVinci Code and Bourne Identity. I know a lot of people think it’s somehow easier to read, but it’s a fairly “standard” book. (I think technically, DaVinci Code has a somewhat lower / easier readability rating than HP 1.)
When you say “somewhat comfortably” I’m assuming you mean an unassisted read of a paper book with relative comfort. In oder to be able to do that, you’d probably need to complete the Advanced 2 level here on LingQ, so at least 35,500 known words, though with Korean, to really read a paper book, you’ll more than likely need to be above 40K known words here. But of course if you’re using the LingQ interface to read it, you can tackle it a lot sooner than that.
I would agree with t_harangi. 40K might be a good level to aim for. But there are many factors that will affect where your actual level is. Primarily your level coming in I would say and any work put in outside of LingQ, be it SRS or other input.
I actually just added HP4 (my first korean HP) to my currently-reading stack. At 84K words and 25K LingQs I can read it rather comfortably and would be able to read it without LingQ. However, there certainly are a decent amount of words that I haven’t come across before or that I only know passively. I checked out my old copy of the English original and there are a lot of adverbs in there and the occasional unusual word so it is not unexpected.
Might be difficult to the evaluate but here are some metrics: after 6 chapters I have around 20% unknown words when I start a new lesson. I usually end up with ~120 LingQs at the end of a lesson (I keep LingQs until I’m very comfortable with the meaning of a word).
To be short, I think Harangi and Wnint are spot on. I’ll give you my experience below because I’ve read the first 4 Harry Potter Books. I stopped because the first 4 are just my favorites in the series 
I’ll add to this a bit because I’ve done the first 4 Harry Potter books off of Lingq. If I match the story with my known words at LingQ, I started doing Harry Potter at around 23000 known words. I’ll also say that since I know the story so well, it was just an excuse for me to revisit it. Realistically, it was not an effective use of language learning time, but I did enjoy myself. This is just part of the way that I like to spend time with languages that many other people probably dislike
In my experience, narrative and formal written styles of Korean use many structures that are rarely, if ever used in everyday contexts. They will make your unknown word count for LingQs much higher. Still, at 23,000 words there was a very high number of unknown words. Even now there is a very high number of unknown words (I currently have 57,000+ on Lingq). I think if you’re using Lingq and you know the storyline well, you can probably start around 25k words and enjoy it. If you’re trying to read off Lingq, I can’t say that I know a great time to start on full on native level novels. Graded readers exist up to the 8000 word level (not lingq words) for a reason. Authors intentionally mix up language use to make the text more interesting to read.
To give you an idea, at my current level I have read several books off Lingq in Korean, but my comprehension level of certain passages is very low if I’m dictionary free. I must say that I find it incredibly fun to learn words without any dictionary use, especially in Korean, where Hanja being replaced by Hangul makes dictionaries just giant lists of words that all look and sound exactly the same, but they are in fact completely different words!
Currently on LingQ, I’ve been working through the 외국인을 위한 한국어 읽기 series available on audioclip. HIGHLY RECOMMEND if you like history/culture When I open lessons there, most have somewhere between 15-25% in the unknown section. After about 10,000 words of reading the majority of content there, about 1-2% end up as lingqs, and the rest end up in my known words because I’ve seen them before countless times and just know them. I also will ignore a lot of the names of characters unless they are a historical figure/author that appears in the Korean dictionary.
Another fun fact, I have had 아몬드 in my lessons for the last 3 months. During this time, my known word count on LingQ has gone up by about 16,000 words, but the % of words on all of those lessons for 아몬드 hasn’t moved from around 26%. I have all sorts of things in my “to read list,” but it’s hard to judge which are truly at my level.
I am aware of the distinction that the Harry Potter books are not easy reads by any means, I just brought it up as it’s easily accessible and the plot is intimately familiar to me. I am currently at 7,254 words and was wondering how much I would need before reading harder fiction literature was reasonable feasible.
I actually wasn’t aware of korean readers, would you be able to recommend me some? I am currently at the 7,254 word mark and I’ve been slogging through 어린 왕자 (the petit prince) day by day. I cover 3-4 chapters a day and it takes me a few hours to get through, the reading is somewhat difficult but I can manage to slog through, I would not want to go any harder than this novel to be honest, one or two steps easier would be perfect for me.
Thanks for all the responses guys, if you have any recommendations for reading material for a ~7k worder please feel free to send them my way 
I prefer reading fiction/stories over anything else, personally.
It’s not “graded” necessarily, but you should check out all of the Talk to Me in Korean Iyagi stories if you haven’t done them yet. There are over 140 of them, they’re extremely natural, and you can get all of the Korean dialogues if you look below the lessons! There are a lot of them already uploaded onto the site here as well, but if you do all of them, you will get to a point where you’ll be pretty comfortable with basic interactions. https://talktomeinkorean.com/
The beginning stories here might be tough, but if you like learning about culture/fables, the beginning ones have great audio and text 오디오클립