The idea for Miss Peregrine's Home popped into Ransom Riggs' head when he ran across some sinister-looking vintage photos, which ''suggest stories even though you don't know who the people are or exactly when they were taken.'' As he began writing, he kept searching for images, even combing swap meets and flea markets. ''I was developing the story as I was finding the photos. I'd find a particularly evocative photo and I'd say, 'I need to work this in somehow.' '' Most are reproduced in the novel ''as is,'' but a few have been digitally altered. Riggs says he ended up with more photos than he could use: ''I have a nice big fat backlog for the second book.''