Alright, I think I got it. New description is:
This book club is intended for people who are just beginning to read native Japanese books and manga, rather than for beginners to Japanese. To be comfortable reading with this book club, you should have a solid understanding of N5 grammar and at least some understanding of N4 grammar. If you’re at that level (or don’t mind putting in more effort), then you should fit in great. If you’re not at that level, check out the Absolute Beginner Book Club. If you’re well above that level, consider trying the Intermediate Book Club.