Signing up for Audible. Offer is $6 per month for 4 months. The four books I'm targeting I already have the previous on audio book format.

Worlds of Honor #6 - Beginnings
https://www.audible.com/pd/Beginnings-Audiobook/B00FN4UJHM

Crown of Slaves #3 - Cauldron of Ghosts
https://www.audible.com/pd/Cauldron-of-Ghosts-Audiobook/B00J5RCL1A

Crown of Slaves #4 - To End in Fire
https://www.audible.com/pd/To-End-in-Fire-Audiobook/B0BKTHNTL4

Star Kingdom #3 - Treecat Wars
https://www.audible.com/pd/Treecat-Wars-Audiobook/B00FW147M4

As I researched this I saw that there is a new Honor Harrington novel, Toll of Honor, coming out in April (hardcover most likely, paperback a year later).