WEST CHESTER, Pa. (WPVI) -- Authorities are searching for an intruder accused of costing a Chester County business thousands of dollars.But this accused thief didn't go after cash or electronics, they went after rare and expensive books.The burglary happened overnight into Sunday at the Baldwin's Book Barn in West Chester."Saw glass on the floor, came in. The books are all gone from the two cabinets," explained Carol Rauch of Baldwin's Book Barn.The casualties were the store's most timeless and irreplaceable books."One was a very expensive book on fish, another one was a German bible with a sterling silver working clasp," Rauch said.Police say they think whoever did this had been here. That's because they knew where to find the most expensive books and exactly how to get to them.Today the store is still open.Rauch says she has full confidence in the West Chester Police to solve this case. But says she might have to delve into Doyle's Sherlock Holmes or the Hardy Boys for a little guidance.The estimated cost of the books taken is around $10,000 to $15,000, but they really don't know for sure. Some of them were so unique there was no way to price them.-----