It is an advanced text; it can be paralleled to the illustrious Book of Abramelin.
Various Grimorium Verum editions and books are available. I recommend the one by Jake Stratton-Kent.
Well, I was inspired by my Goddess Kalika to dedicate my time to completing Grimorium Verum evocations (GV operation, as I refer to it).
I read through all the text lots of times, really dedicated my time to trying to comprehend the essence of the text, and I decided to skip the tedious medieval preparation instructions (you will know what I mean when you read the book :) ), knowing that those material deeds and tools may or may not be crucial for the operation. Such preparations accumulate a lot of energy, though, so going through with them may be a good idea. Not me, however. I am not a traditionalist and love to improvise.
I have a lot of experience working with spirits and Goetia evocations, and I employ no tools (circle, triangle, ring, etc...), and it works out very well. Besides, Abramelin's operation is stripped bare of all material tools apart from a consecrated space, wand, and oil. The GV operation can be concluded in similar ways. My Kalika was there with me all of the time.
I followed inner inspiration and commenced the GV operation on Thursday last week; I did it in my office (where I usually perform various magick rituals, Aethyrs visiting, etc...); I consecrated the place with Abramelin oil and drew a circle with my wand around my seat. Pure white energy was pouring out of the wand like a laser beam. I also offered incense to the spirits I was about to evoke...
I also had all the sigils outlined in the book printed on an excellent paper. I intended to request spirits to sign their respective sigil, thus taking an oath of allegiance to me. I understand this to be equal to requesting the spirits from the Abramelin operation to swear on the word squares.
According to the GV, there are three Kings, six Deputies, and various powerful subordinate spirits - all under King LVX Ferre and his emissary, Scirlin.
With the above character (according to the GV book) in my left hand, I first evoked Scirlin. I immediately saw a change in the room, and upon my request to see it in human form, I saw a lovely lady. It was Scrilin. I knew that a relationship with her was the key to a successful GV operation, so I took some time to establish a base for a friendly relationship with her. No threats, no "if you don't deliver, I will..." etc..., just clear thoughts and intentions. Initially, she was unwilling to cooperate with me, but the situation changed when I focused on my Devi, Kali. I also kindly let the Emissary know that the incense is also burning in her honor.
From my Tantric practice, I know that most spirits are miserable and covet the elemental energies, which can be offered to them via incense, water, fire, oil or perfume, and flowers or food or stones. According to the Tantric tradition, spirits have no mouth, so they "eat" via the sense of smell.
I also offered her fire (and a powerful perfume later on in my apartment), and she was most pleased.
I moved on with the evocations, starting with the great king, LVX Ferre.
I will refrain from outlining the details; let's just say that we are "friends" now (GV says that "spirits will offer their service to those that have good relations with them and are 'friends'"; I am paraphrasing here of course).
The relationship with Scirlin and later with LVX Ferre introduced rather intense transpersonal realizations regarding the nature of the spirits.
GV operation completed
To make a long story short, Scirlin was on my side, and spirits listened to her, some slightly intimidated by her, some more rebellious but still willing to cooperate.
They charged their respective sigils (or, as the GV says, they sign the sigils), thus making themselves available.
Just today, I summoned Scirlin and asked her which spirit would be particularly good for my task, and she suggested Elantiel. I summoned him, or she called him over; he was docile and willing to assist me. He even asked some questions. The operation was a total success.
That was it.