All three titles in the "classic Heorot series from genre legends Larry Niven, Jerry Pournelle, and Steven Barnes" (to quote the series page) are free right now at Kindle UK.
Titles are:
- The Legacy of Heorot
- Beowulf's Children
- Starborn and Godsons
Link to the series webpage:
https://www.amazon.co.uk/gp/product/...ies_rw_dp_labf