Add content from one content type into another content type
You can achieve this using reference module

Install this module, enable the references and node reference checkbox in the Module menu.

Create the people and book content type with the respective field

In Book content type, Add the People name field, and choose the node reference , then it will the show all the content types.

Select the People content type, set the widget types as select list.

Then create a content in Book, People Name field will show the people title as options in select list..

DO this thing, Please ask me if you have any queries.

Before that: Create some contents in People content type.