I will write down a few notes about the novel you should know. Although they are spoilers, it will help a person understand the worldview. Also, the information here will be updated as the story progresses.
1 - The Primeval World – this is a library where Book Lords store their grimoires, but unlike a normal library they can store none-living objects which have spirit essence in them. Unless a grimoire is involved things like a phone car not be stored in the Primeval World.
2 - Qi – a very harmful intangible, invisible form of energy that ignites spells in grimoires. Qi can only be stored in the Primeval World, and if it invades the body, one might be led one to be a cripple, or worse, death, depending on the amount. (10 grams of Qi can make a person explode.)
3 - Grimoires – Spirit books needed for activation of a spell. Each grimoire can use one spell at a time. As long Qi is infused into a grimoire at a constant pace, a spell will keep going unless they are any external factors. No matter what, a person can never read the worlds written in a grimoire except for the word "Denga" meaning (Space), this is the reason why spells happen outside the primeval world, when Qi is infused into a grimoire. To make a spell, Qi that is infused into a grimoire and converted to spirit essence.
4 - Spirit Essence – The form of energy found in spells, and is very friendly with the human body. When Spirit Essence gathers it creates spirit crystals.
5 - Spirit Crystals – Money/ Currency. Spirit crystals can help a person replenish the Qi in ones jindan.
6 - Jindan – The storage Area where Qi is stored before it is used on spells.
Book Lords – They are divided into four branches. There are those who want to cover all categories, but for those who pick one (the majority) will either use the other three as sub-branches.
Warlock – Those that use spells to affect the surrounding area and people.
Mentalist – Those that use spells to affect the mind. If you are wondering which type of people here is some examples, those that engage in taming and divination.
Shaman – Those that use spells to affect the soul, like necromancers and puppet masters.
Martial Artist – Those that use spells to affect their own bodies and weapons.
— Book Lord realms – each realm has five stages with the 1st stage being the weakest, and 5th stage being the strongest.
— Spirit realm (beginner)
— Human realm
— World realm
—Legend realm
—Transcended realm (peak)
— Profound Beast are animals which can gather Qi by their own bodies naturally with their bodies, just like how a wild grimoire can feed itself before it is in the hands of a book Lord. Profound Beast only have realms, and just like grimoires they don't have stages.
— Elementary
—Novice
— Core
— Battle
— Monster (peak)
• Grimoires and Spirit Weapons all share the same realms as a Book Lord.