You are in a room with 3 digital weight scales and a big book. The digital scales are small like the ones you see in small stores. They are identical in all aspects. They all have a READ button which when pushed gives you a weight reading for 1 second. Readings are in whole pounds, not fractions.
One scale is accurate.
One scale always gives 1 pound less reading.
One scale always gives 1 pound high reading.
By taking only TWO weight readings determine which scale is accurate, which one gives lower reading and which one gives higher reading. No, you cannot stand on the scale!