* The Highlander Series: 10 books
* The Fever Series: 9 books
* The Darkfever Series: 5 books
* The Bloodfever Series: 3 books
* The Dreamfever Series: 3 books
* The Shadowfever Series: 2 books
* Other standalone novels: 2 books
Note that some of these titles are part of the same overarching series, just with different names for the sub-series.