Although I haven’t read any of these books, some folks on an e-reading forum I belong to (MobileRead) like the John Jordan series by Michael Lister. And books in the series tend to go on sale/free pretty often – including sometimes some omnibuses that will give you several books at once for a free or discounted price. So that’s kind of nice. If you’re interested, keep an eye out here, and I’ll post in the comments when I see any of these on sale or free in the future.
And right now, Innocent Blood (a prequel, although it’s the 7th title in publication order) is free at Kindle US and UK.