There are a couple of ways to tell that the reading is from a book (and e-book! e-book citations and print book citations are normally identical in APA 7th) and is not an article from a journal.  

• There is only the title of the book and not a title plus another title.
• The citation may include an edition.
• The citation doesn't include a volume, issue, or page numbers.
• Book citations will have the name of the publisher.  Journals will not.

Below is an example book citation:

Shushkewich, V. (2003). The real Winnie: A one-of-a-kind bear. Natural Heritage Books.

Breakdown of the citation:

Author:         Shushkewich, V.

Year:            2003

Book Title:      The real Winnie: A one-of-a-kind bear

Publisher:      Natural Heritage Books