I just published a Kindle book. I was unable to use the KDP Select program because I had serialized the book here first. KDP Select would have allowed me to give the book away for free for a while and thereby gain some word of mouth and some traction on the sales ranks.

it depends on which you are going to prioritize; precence on Steemit, or book sales.

Finally, you may want to ask someone at the publishers about how much of the book can you give away? Perhaps a sample chapter or two?

Good Luck!