The Dark at the End is the final book in the Repairman Jack series. But it's not the final book where Jack plays an important part.
This book follows the others in the series like one continuous novel. The difference is this is the last in the series and I would have thought it would be a conclusion. Nope. Nightworld, the last book in The Adversary Cycle series, will be the conclusion to the Repairman Jack series as well.
Nightworld is not available on the kindle, and even a paperback will cost you almost $60 new. I guess I'm not finishing this series :) I highly recommend The Dark at the End, even though you'll still be hungry when you're done.