It might also help to know that if you buy the ebooks directly from JNC instead of from Amazon, etc. there is bonus content:
https://forums.j-novel.club/topic/305/premium-e-book-bonus-contents-list/
Volume 1: Alternative Cover, Pinup, Bonus Image, 6 store exclusive short stories
A Man's Dream
The Holy Goddess' Descent unto Paradise
A Case of What If
A Nightmare in the Abyss
The Liberators' Game
Dreams of Family
The bonus content is only in the published ebooks, not in the pre-publication versions you can read on the website. When titles are on "catch up" for the month (like Unwanted Undead for October) they are still the pre-pub versions NOT the ebooks with bonus content.