a art book还是 an art book

是an art book，例如：

1、In his free time， he runs an art book publisher， Teknisk Industri.在闲暇时间，他经营一家名叫TekniskIndustri的艺术书籍出版社。

2、Straighten up your periodicals and put out an art book to show you're more than a pretty face.把你的期刊杂志清理掉，摆放一些艺术书籍，向他们展示你不仅仅拥有一张美丽的脸蛋。