in which the warp drive theory chosen by Elizabeth Bear in this book (and its companion, set in the same universe but so far as I can tell, not directly related) is described.

Some fun bits

Miguel Alcubierre, a theoretical physicist in 1994 developed a theory called the Alcubierre drive. He created a bubble within space-time that would twist distances making it possible for anything to travel long distances within the bubble. Most people thought this made perfect theoretical sense, but practically it wasn’t workable.
...
[it] would require a large amount of mass-energy to make the warp drive function. To propel the spacecraft at such as level, you would need the mass equivalent to that of Jupiter.
...
Dr. Harold Sonny White, a NASA mechanical engineer, and physicist is still trying to find ways to solve the mass-energy that is required. He believes by bending ways in physics, it is likely possible to bring down the mass-energy requirement mentioned in the Alcubierre theory. He also suggested there might be slight possibilities to change the shape of the ring of the negative mass to enable mass requirement of about 700kg.
White is now leading a team of physicists and engineers in NASA to build the White-Juday Warp Field Interferometer. It is a beam splitting interferometer which can easily detect and generate the tiniest warp bubble. Perhaps this might not instantly get you over to Andromeda Galaxy, but eventually, you’ll get there when needed.

Haimey Dz thinks she knows what she wants.
She thinks she knows who she is.
She is wrong.

A routine salvage mission uncovers evidence of a terrible crime and relics of a powerful ancient technology, just as Haimey and her small crew run afoul of pirates at the outer limits of the Milky Way and find themselves both on the run, and in possession of ancient, universe-changing technology.
When the authorities prove corrupt, it becomes clear that Haimey is the only one who can protect her galaxy-spanning civilisation from its potential power - and from the revolutionaries who want to use it to seed terror and war. But doing so will take her from the event horizon of the super-massive black hole at the galaxy's core to the infinite, empty spaces at its edge. Along the way, she'll have to uncover the secrets of ancient intelligences lost to time as well as her own lost secrets, which she will wish had remained hidden from her forever . . .

Energetic and electrifying, Ancestral Night is a dazzling new space opera, sure to delight fans of Alastair Reynolds, Iain M. Banks, and Peter F. Hamilton.