The second book, "Midnight Oil," introduces a few additional characters such as Mordita the Sorceress, Ceto the Loch Ness Pleiosaur, Atlantis (also called Ultima Thule), an evil forest spirit bent on destroying her own sister, and many more.
The final book, "Scotch Broom," follows Katrina into the Scottish Highlands Otherworld--a place for magic creatures to live in when humans just become far too much bother.
After the three main books in the series, I added a prequel story about the other major character in the books. Rune, Kat's half brother. They share their mother Ardyth, but have different fathers. Kat's dad being a mundane but very handsome Sami warrior and Rune's being a just-turned vampire named Drakos. The prequel story, "Spellslinger," is Rune's tale of testing his own magic and becoming aware of the danger inherent in his vampire half.
"Scotch Broom" leaves Rune in a bad mental state. I don't want to give spoilers, because you people really ought to read the series.
Rune's troubled mind required one final tale, "Blood Ties Tested." Rune finally meets his vampire father. Together, they go on a rescue mission for a group of reformed vampires captured by the great grand nephew of Van Helsing, the famous vampire hunter.
So, ebook done, print book done. Now the audiobook version is in the works and will be released sometime in late May (if all goes according to plan). It'll run about 2-1/2 hours and will accordingly be priced fairly low. It'll be available on Amazon, Audible, and iTunes. The best deal will always be at Amazon, where audiobooks are discounted if you buy the ebook to go with. The ebook and audiobook will be whispersynced, which means you can switch back and forth between reading and listening.