This article has a great tip on reading non-fiction: do not read non-fiction word-for-word like fiction books. Fiction requires that the reader immerse in the author’s world. Non-fiction tries to convey an idea.

Here is method from linked article.

1. Start with the author
2. Read the title, the subtitle, the front flap, and the table of contents.
3. Read the introduction and the conclusion.
4. Read/skim each chapter.
5. End with the table of contents again.

See the original article for the full explanation of the method.