Just finished reading this.
Excellent read, really good stuff. The main character is this Zen-like wormhole-wielding, sword-bearing, 1000 year old, fully backed up ex programmer with an AI avatar in a black cat companion who travels the created pocket universes studying the implied spaces within them for fun.
If that doesn't draw you to the book, read a real review. Then you would miss out on massive rail guns, antimatter sprays, zombie plagues, battles, death, resurrection, and AI shenanigans.
The book is very readable, well written and fast paced. I'll be reading more of Walter Jon Williams work for sure.