The Murder Book: 10 Complete Crime Novels, edited by Michael Lister, appears to be pretty much what it says it is...and it's free right now at Kindle and Kobo US.
Three of the titles in this omnibus are listed in
SYKM (which is sort of my fast check on self-pub or not when I'm in a hurry) -
Blood Oath by Michael Lister,
The Dying Hour by Rick Mofina, and
Circling the Runway by J.L. Abramo, which (also per
SYKM) won the 2016 Shamus Award for Best Paperback. A couple of the other authors' names (Jeff Shelby, author of the Noah Braddock series, and LA Dobbs) ring a bell in my brain but their specific titles aren't in
SYKM, and the rest are new to me, but WTH, the omnibus is free.
Kindle US:
https://www.amazon.com/Murder-Book-C...dp/B07CGNTB4G/
Kobo US:
https://www.kobo.com/us/en/ebook/the-murder-book-6