I recently found that Faber and Faber, an independent UK publisher, has a large selection (129 to be exact) of their books free on Kobo right now. Among them are Andrew Martin's Jim Stringer series including his most recent one released just this month. One I purchased a few weeks ago is now free as well. It was Hit and Run by Doug Johnstone and I highly recommend it. I've posted the link below to the search filtered by free only.
Faber and Faber