The other part to this is: how do you look up an unknown kanji? If it’s in your browser then there are extension for that. If it’s on your screen there’s ocr scanning options (on screen reading, I like YomiNinja but there are others.) And obligatory KanKan is great for searching by radical if it’s a compound word where you know one kanji and not the other
If it’s a real physical book? You can take a picture and go back to OCR…or you can search by radical, which works when you know your radicals and it’s not too many kanji at once, but it’s a pain if it’s half the kanji.
Also Natively has rankings for how difficult manga and other books are, so it’s a valid strategy to start with easier books and work your way up, but the early levels can get boring.
Personally, I started at 24 (after having read through genki 1 and 2 putting me at ~N4 grammar). It was slow and I was looking up a lot of things, but I tried writing down everything I looked up. It gets faster over time. I’m still (at currently level 55) looking up a bunch of new vocab, but vocab is a lot easier when I know most of the kanji and it’s just combined in a new way. I also wrote down the wanikani levels for any vocab (I used 10ten browser extension to do this quickly). It was extremely gratifying to be level 24 and tell myself "well 靴 is level 27, 恐ろしい is level 29, 捨てる is level 32…but there were lots of words like 校長室 that aren’t on wanikani, though you learn all of those kanji by level 7, so they weren’t hard to look up. I’m playing games that I enjoy anyway (and aren’t on a timer, so I can pause and search for kanji for 5 minutes if I need to), but because I’m interested in them it’s a lot easier to sink 10 or 100 hours into playing them slowly than an easy manga where I’m less invested in the plot.