Heaven Is Gentle by Betty Neels
Sister Eliza Proudfoot took a job at the special clinic run by Professor Christian van Duyl. She found him a somewhat formidable character - large in build and large in personality! He wasn't precisely overbearing, but Eliza somehow kept getting on the wrong side of him - a mistake when he was engaged to the very suitable Estelle van der Daal. Eliza found Estelle a bit of a bore, but if that was what he wanted, who was Eliza to quibble! Was Estelle really suitable - or was Eliza kidding herself that she might stand a chance with him?