Right now my grammar knowledge basically consists of all of N5/N4, a lot of N3, and some more from exposure when reading. My vocab knowledge feels very sparse but I have no idea how to quantify it. Basically whatever I learned from WaniKani, Core 2000, and exposure from reading.
My question for people with extensive reading experience is: from where I’m at now, is grammar or vocab more important to improve my reading speed and comprehension? Right now it’s basically impossible for me to read an adult-targeted book or light novel in less than a couple months (because of time to look stuff up, parse sentences, and ultimately burnout). I can easily read a 300-500 page English book within a few days (a week if reading leisurely), so to start I’d like to get to the point where I can read a 300 page Japanese book within a month or so with good comprehension.