Charles did want to get to work soon, but the way he saw it the more familiar he was with the Doctor's facilities the better he'd be able to carry on in the future. It wouldn't do to constantly interrupt work to have to ask where things could be found, and getting a handle on what the TARDIS was capable of would help him by telling him what the available resources were.
"I do try to be a man of learning. A bit too much of one, if you ask my sister." Charles said, self-deprecatingly, but with a definite note of fondness for Raven. He considered the Doctor's question seriously, knitting his fingers behind his back as he mulled it over.
"I'm going to shock you by saying the library, I'm afraid," he laughed, taking the stairs with the eager agility of a child on Christmas morning barely restrained by his awareness he was a grown man with a Ph.D. and thus certainly supposed to be above such things. He'd been criticized in academia before for his attitude, and it would be a shame if he made a poor impression so early on.