Perhaps the complete but simple message of You Can Share the Faith could be summed up with this short passage from In This House of Brede:
Nowadays there's a tendency to make everything utilitarian--even the things of the spirit," said Dame Claire. "Beware of this," and, "That wasn't the way of the saints," said Dame Ursula. "They didn't set out to be of use."
"Nor they did," said Hilary in surprise.
"And you needn't worry about being useful," said Dame Ursula. "'When you have become God's in the measure he wants, he, himself, will know how to bestow you on others.'" She was quoting St. Basil.
I finished In This House of Brede about a week and a half ago. Expect an avalanche of quotes.