Inhibitor Phase is the fourth and most recent novel in the Inhibitor Cycle, the main narrative sequence in the Revelation Space universe.
Prior to release
An 18 page excerpt was included with the trade paperback of Bone Silence.
The book's completion was announced by Alastair Reynolds on his blog, October 8, 2020: https://approachingpavonis.blogspot.com/2020/10/ive-delivered-book.html
The word count is 170,000 (Reynolds contrasts it to Absolution Gap's 275,000 words).
Included in the blog post is a teaser word cloud, with some words too small to be visible. U.K. publisher Gollancz targeted August 26th, 2021 as the release date and ended up releasing on [insert date here]; U.S. publisher Orbit targeted a publication date of July 27th, 2021 but actually released on [insert date here].
[here be spoilers]