Q: Is it that we can only write the summary of a book?

Note that your question didn’t seem very clear, so we have made some edits. So, it seems you’d like to know whether an author (a research author in our case) can only write the summary of a book (an academic book in our case).

The answer, quite simply, would be: Not, not at all. You can also write the summary of an/your article. For instance, the abstract is a summary of sorts. Then, you can also write a lay summary (or plain language summary), which is a summary of your article for the benefit of the public and not just researchers. You can also summarize your thesis/dissertation, such as when applying for a research position or job.

For more on summaries, you may find it helpful to go through the following resources:

• How can I write a proper summary?
• How can we write a summary of a thesis?

Hope that helps. And in case you’re planning a summary, all the best for it!