Each time I click an "href" link it adds the link again to the URL. Why?

I've got a button that says

<a href="home.jsp">Home</a>

and another link

<a href="CRUD/Books/Add.jsp">Add</a>

If I click Home then Add it works fine but then when I click add again the URL multiplies like this

URL: CRUD/Books/Add/CRUD/Books/Add.jsp

and I have lots of pages with the same issue what should I do to prevent this?