Q: How do I write an inquiry to a journal about publishing a chapter in their upcoming book?

Journals usually publish articles, not books. I don't think you can make an inquiry into a journal about a book chapter. Books are generally published by academic book publishers. You will need to find out which are the leading publishers of academic books in your field.

Take care to choose only those publishers that are reputed in your field. Please cross check with your supervisor, professors, and senior colleagues before you submit your book chapter. This is because there is an emerging breed of predatory book publishers who target naive authors. Once you identify a reputable publisher, the process is similar to sending a pre-submission inquiry to a journal. In your email, explain what your book chapter is about, mentioning what kind of book would be suitable to publish it in and who your target audience is.

Another way to publish a book chapter is to collaborate with other authors from the same field and plan out a book in which each person contributes one or more chapters. Once all the chapters are written, you can approach a publisher together.

Related reading:

• Should I accept an invitation to publish my journal article as a book?
• Should I accept an invitation to publish my academic work as a book?
• How to write a pre-submission inquiry