A grimoire covers such topics as making amulets and talismans, summoning spirits, casting spells and charms, and all that other stuff you can learn at Hogwarts. The implication is that what you’ll learn to do is secret and occult and not meant for everyone, particularly not squibs or muggles. (Yes, I’ve read them, and quite enjoyed them, and I’ve even watched the movies. So what?)
I have no experience with that kind of grimoire, as you can probably imagine. However, there is a set of books that I was sorely tempted to buy back in my guitar-playing days, namely The Guitar Grimoire series.
Back in the days when there were bookstores that sold books like this, I would pick this book up and flip through it, then think, “Wow, this book will teach me everything I need to know to become a guitar genius!” I’d spend a good half hour looking through it, and eventually realize that I could likely produce the same results by applying what I already knew about music theory (one class in high school) and about the guitar (specifically where all the notes were on the neck, which I learned when I was eleven and took my first couple of guitar lessons), provided I planted my fat ass in a chair, picked up my guitar, and set about the task of learning all of it. That would cost me nothing, whereas the book cost about $25, and I’d still have to plant my fat ass in a chair, pick up my guitar, and set about the task of learning it.
I’m not saying that these books are useless and a waste of money. If owning the book gets someone who wants to learn to play the guitar to sit down with the instrument and actually learn the material and how to play, then it’s worth every penny. The same thing is true for any book, music or otherwise: if you actually care enough to learn the material and are faithful to using it, then it’s money well spent. Simply owning a book isn’t going to magically endow you with the ability to play like Eric Clapton, or to write like Eudora Welty, or to sell like Og Mandino, or invest like Warren Buffett.
I think we all fall victim to that kind of thinking, to a greater or lesser extent. I know I do.