For those who have KU, Harlequin, MacMillan, and other publishers have been putting a lot of books in the program (unlike self-published authors they don't have to be exclusive to Amazon).
A few I've seen are:
- The Blackberry Bay trilogy by Shannon Stacey (More Than Neighbors, Their Christmas Baby Contract, The Home They Built)
- Polaris Rising by Jessie Mihalik (Consortium Rebellion #1)
- Deal With the Devil by Kit Rocha (Mercenary Librarians #1)
But there are probably a lot more.