Three of CJ Box's books are gathered in an omnibus called
The Big Sky Collection. Two feature Cassie Dewell/Cody Hoyt:
Three Weeks To Say Goodbye and
Back of Beyond. The third is a non-series title,
Blue Heaven, which, per
SYKM, won the 2009 Edgar Award for Best Mystery. The collection has dropped to £0.99 at Kindle UK. This collection doesn't seem to exist in the US, but a similar four-book collection, which also includes
The Highway, is currently $27.97 (!!!) in the US.
In addition,
Blue Heaven is also available individually right now at Kindle UK for £0.99.
And finally, Box's
Winterkill, which is the third in his Joe Pickett series, is on sale for $1.99 in the US.
The Big Sky Collection
Kindle UK:
https://www.amazon.co.uk/gp/product/B009E99DRY
Back of Beyond
Kindle UK:
https://www.amazon.co.uk/gp/product/B003V4ASZY
Winterkill
Kindle US:
https://www.amazon.com/gp/product/B000OIZUWQ/
Kobo US:
https://www.kobo.com/us/en/ebook/winterkill-1