For the first place in the shlef you have 5 possibilities to choose, for the second place you have 4 possibilities, for the third you have three possibilities and so on. This means that we can find the number of ways to arrange the books with a factorial, that is:
![5!=5\cdot4\cdot3\cdot2\cdot1=120](https://img.qammunity.org/2023/formulas/mathematics/college/878c47q22bjvwbokeoaxg9kq7srjyw7gqp.png)
Therefore, there are 120 ways to arrange your books in the shelf.