In a Blue Velvet Dress — Catherine Sefton

The girl was standing by the window, looking at the lavender, her small white face solemn.
"Hello," Jane said bravely.
The girl turned slowly, gave a small smile...and disappeared.

Jane Reid is a bookworm. So, when her parents sail off to Scotland, leaving her with the bookless Hildreth's, Jane is soon bored. Then, as if by magic, a book appears on her bedside table...and the next night, another one... But how and from whom?