Apologies to the scientists.
In some disciplines in the humanities and social sciences, publishing a book is almost expected, despite widespread debate about whether it is reasonable to do in the current publishing economy (e.g. this MLA report).
A book may be required for you to get tenure but that doesn’t necessarily mean that the book is the best thing to do right after defending your PhD. You need to get a tenure-track job first. And in the current labour market, you need publications to even get in that race.
Evaluate what you have.
My own book is substantially the same as the dissertation. The revisions took me a couple of months and the book was in print within a year of my examination.
If you can do that, do that.
If, on the other hand, you need to do additional research to make this a publishable monograph then this is not your “dissertation book”. It’s your next project. Don’t put off publishing something from your dissertation while you get on with that next project.
What can you publish right away?
You are publishing to make a contribution to knowledge. Assume that no one will read your dissertation that didn’t have to. How do you get that knowledge out of your head and into the debates in your field?
You could take the model that many scientists treat as the default: your dissertation is three journal articles. Take the main substantive chapters of your dissertation and rewrite them into stand alone articles with their own introductions and arguments. This approach assumes that the book will be a different project.
Write an article length version of your main argument.
You will support the argument with some of the empirical material but this is more like a taster for the eventual book length version than a replacement of it. You might publish one of these even if you can revise the dissertation into a book quickly. (I did that, too.) This doesn’t compete with the book but might bring new readers to the longer text, and make it easier for others to include your work in their syllabi. More readers = more impact.
Write a journal article based on one of the dissertation chapters.
There may be a stand-alone contribution to a particular debate there that is different from the role of this chapter in the overall argument of your dissertation. This doesn’t compete with the book either.
Write up one of those ideas that didn’t end up in the dissertation as a journal article.
You have at least one of those, right? A conference paper that you abandoned, maybe. In fact, now that you’ve finished the dissertation, go find all those orphan projects and make some decisions about which ones to pursue.
Your dissertation is the beginning of your research career.
Start to think of it as one stage in a longer process. Publish what you can now. Plan the book and the additional research that it needs. Then get started.