All three books are unmarked and include answer keys and explanations. There are no markings in the social studies book. In the math and science books, pencil markings have been erased, but there are a few places where problem numbers are marked with a ballpoint pen. Instant purchase is OK. Selling individual books is OK. Buying multiple books is OK. I am also selling other reference books, so please take a look. If you have any other questions, please leave a comment!