1. A book scanner, comprising: a housing; a carriage moving in reciprocating motion in said housing, wherein an original is placed on said book scanner and scanned with a scanning module disposed in said carriage; a transparent platen disposed on a top of said housing, wherein said original is placed onto said transparent platen; and a light source having a substantially strip-shaped light tube disposed in said carriage and corresponding to said transparent platen, wherein a light beam from said light source transmits through said transparent platen and illuminates said original, wherein said transparent platen comprises a first light transmission part and a second light transmission part, both said first and second light transmission parts are configured adjacently to form an angular structure, a crest line is formed along a joint of said first and second light transmission parts, and said strip-shaped light tube is lengthwise perpendicular to said crest line, a scan area is defined on each of said first light transmission part and said second light transmission part, said original is placed within said scan areas, two ends of said light source exceed a boundary of said scan area for each of said first light transmission part and said second light transmission part.