var img1=new Array(new Image(), new Image());
img1[0].src="images/books_1.jpg";
img1[1].src="images/books_over_1.jpg";

var img2=new Array(new Image(), new Image());
img2[0].src="images/books_2.jpg";
img2[1].src="images/books_over_2.jpg";

var img3=new Array(new Image(), new Image());
img3[0].src="images/books_3.jpg";
img3[1].src="images/books_over_3.jpg";

var img4=new Array(new Image(), new Image());
img4[0].src="images/books_4.jpg";
img4[1].src="images/books_over_4.jpg";

var img5=new Array(new Image(), new Image());
img5[0].src="images/books_5.jpg";
img5[1].src="images/books_over_5.jpg";

var img6=new Array(new Image(), new Image());
img6[0].src="images/books_6.jpg";
img6[1].src="images/books_over_6.jpg";

var img7=new Array(new Image(), new Image());
img7[0].src="images/books_7.jpg";
img7[1].src="images/books_over_7.jpg";

var img8=new Array(new Image(), new Image());
img8[0].src="images/books_8.jpg";
img8[1].src="images/books_over_8.jpg";

var img9=new Array(new Image(), new Image());
img9[0].src="images/books_9.jpg";
img9[1].src="images/books_over_9.jpg";

var img10=new Array(new Image(), new Image());
img10[0].src="images/books_10.jpg";
img10[1].src="images/books_over_10.jpg";

function swap(img, on){
	document[img].src=eval(img+"["+on+"].src");
}