Since it is intended as a reference book, my suggestion would be to place it where it is needed (if possible): on top of King’s Market. Of course it would be good to make this book also craftable.
I was thinking of maybe writing two more texts for ingame books. One for rather impatient, impulsive players that might start with the paragraph “How to get rich by trade”. For this book I would suggest that it can be both found and crafted.
Another idea for an ingame book would be one with advice for the aspiring advanced trader. Here, for example, I would cover advice on sensible pricing and maybe even things like merchandise value leverage and speculative investing. I imagine that more sophisticated players would also like to learn about things that (can) work in real markets as well. I would suggest this book as a craftable-only book.
Please let me know what sounds usable to you. 🙂