Adds monitoring modern infrastructure

free-programming-books.md

@@ -300,6 +300,7 @@
 
 #### Cloud Computing
 
+* [Monitoring Modern Infrastructure](https://www.datadoghq.com/ebook/monitoring-modern-infrastructure/) *(account required)*
 * [Multi-tenant Applications for the Cloud, 3rd Edition](http://www.microsoft.com/en-us/download/details.aspx?id=29263)
 * [OpenStack Operations Guide](https://docs.openstack.org/ops-guide/index.html)