The hollow places : a novel By T. Kingfisher
"Pray they are hungry. Kara finds the words in the mysterious bunker that she's discovered behind a hole in the wall of her uncle's house. Freshly divorced and living back at home, Kara now becomes obsessed with these cryptic words and starts exploring this peculiar area--only to discover that it holds portals to countless alternate realities. But these places are haunted by creatures that seem to hear thoughts...and the more one fears them, the stronger they become"--Provided by publisher.