You need a broad overview
There are times when you want someone to explain everything to you - beginning to end. Books are very appropriate for this.
Example: An overview of the legal, moral and medical issues surrounding right-to-die

 The topic is very recent
Books take an awfully long time (years!) to get published, purchased and put on library shelves. If the issue you are researching is constantly changing, a book may be outdated by the time it arrives in the library.
Example: The latest information about the parental consent debate for underage abortions

 Your research topic is historical
Books lend themselves to topics in which the facts don't change much over time.
Example: A detailed account of the development of the civil rights movement in the United States

 You have a fairly narrow topic
Sometimes books just cover too much and offer too many perspectives.
Example: The theme of isolation and desperation in Charlotte Perkins Gillman's "The Yellow Wallpaper"

Single publication providing in-depth information on a specific, usually scholarly, subject written by experts in the field for an audience of their colleagues.

You might be reading a scholarly book if...

• It was published by a university press or academic publishing company
• Sources are cited and there is a list of references at the end of the book
• The author(s) have degrees in the field they are writing about and are (usually) associated with an academic institution

Good for when you need verified, in-depth background information.

Good for when you need in-depth analysis of a broad topic or lengthy period of time.

Fictional books written for a general audience.
Usually written as a narrative using prose, or natural language.

You might be reading a novel if...

• Sources are not cited throughout the narrative and there is not a list of sources at the end of the book
• It tells a story using literary elements like characters and plot

Good for when you are writing a literary criticism or review of the book.

Good when you want to read for personal enjoyment.

NOT good as a scholarly source for a research paper.

Publications that provide a broad overview of currently accepted knowledge within a particular academic subject for the purpose of explaining it to new learners.

You might be reading a textbook if...

• The author spends a lot of time explaining the content or material
• It contains sections with review or practice questions
• It was published by a textbook publisher

Good for when you are just beginning to learn about a topic and need a broad, easily digestible overview.

Good for gathering background information and gaining an initial understanding of a subject.

Publications that contain general summaries, definitions, statistics, etc. on a broad subject area and is organized for easy information retrieval.
They are often published in multi-volume sets.
Examples of reference books include dictionaries and encyclopedias.

You might be reading a reference book if...

• There is an index directing readers to specific entries
• Content is organized logically (usually alphabetically or chronologically)
• Content is broken down into short entries providing a very brief overview on many topics

Good for when you are just beginning your research and need a basic understanding of your subject.

Good for when you need to look up quick, factual information.

Can help you find additional, more in-depth and/or scholarly resources.

Books that contain a collection of shorter written works.
Can consist of a combination of articles, essays, poems, short stories, etc.
All content usually share an overarching theme or have underlying similarities.

You might be reading an anthology if...

• There are many shorter, individual works included in the book
• The included works share a common theme, time-period, format, or author

Good for finding short stories or essays that may be difficult to find published elsewhere.

Good for comparing and contrasting similar works.

Can be good for getting a variety of perspectives on a single topic.