Merlin made a thinking noise. "At least a few thousand," he said, looking up at the three stories and trying to estimate by looking. "They are generally grouped into subject, but I read something and don't always put it back where it came from. The books down here are the ones I want on hand if something comes up." He felt fairly certain that Rosario would be able to come up with some sort of organisation system, and then he could implement it himself.
"And these," he added, going to another pile from the floor and setting them down onto a trolley nearby with a thud, "are for you. Just a kind of eclectic overview, but I think they would be helpful. You need to know the basics before you can really get a handle on your gift."
A book on meditation. One on the history of prophets. Dream symbolism. A book about his own stories, for inspiration. Ancient Greek oracles, and also of mythology. A few others, in a mix of subjects that could all be relevant or at least interesting to Rosario and what she was dealing with. Or maybe no help at all, but at least it was there if she wanted it.