The main barrier to reading comprehension is grammar, as opposed to vocabulary, I think. Vocabulary is relatively quick to look up if you don’t know it, whereas if you don’t understand a grammar point, that can take more effort to learn. Of course, the more vocabulary and kanji knowledge you have, the easier it will be to tease out meaning from a sentence, but if you haven’t been studying grammar as well, that is the biggest barrier, in my opinion.
I joined the Absolute Beginner Book Club (at the time, the selected book was Teasing Master Takagi-san) at around mid-20s in WK, and armed with knowledge of most N5 and N4 grammar points, having studied using videos like those from Cure Dolly or, more commonly (the voice of Cure Dolly was just too grating for me), Japanese Ammo with Misa.
I recommend to join one of the book clubs whenever you start to read; it’s been the single most helpful thing in jumpstarting my learning. Of course, this is only true if the selected book catches your interest, as caring about what you are reading means you’ll be more determined and patient in figuring out meaning.
Also keep in mind that if a book you want to read has been selected as a club in the past, you can always post in the threads anyway, even if the club is technically finished with the book. Often, people will have the threads set to watching and will be happy to come back and answer any questions you may have! 