In Book 2, a Lifedrainer, a monster of Bubbleland legend, is tracking some or all of them and kidnapping other denizens of Mudflat while it searches. Nance, Tarvik, Claire and Claire's cousin Jimmy go to the Cascades, find and destroy the Lifedrainer, and return to Mudflat to a hero's welcome and even more questions. One of those questions was resolved when Ober showed up to find out who killed her Lifedrainer.
In Book 3, Deathwalker (who was not killed, but was buried by Lor, the helpful stable guy from Book 1) has shown up to try to find his boss Ober, or at least some magical item which will give him access to her power(s). Deathwalker enchants some people (including Tarvik) while everyone else scurries around trying to figure out where the magical item is. Turns out Deathwalker is allergic to plastic, which leads to a completely hilarious climatic battle scene at Sergei's house. The amulet is discovered later in a hilarious anticlimatic scene involving bicycles. All seems resolved, except we still don't know who cut the brake line in Claire's beater car.
Over the course of the three books, Claire's very limited magical power has been developed. She has essentially no offensive or defensive powers and there are a lot of limitations (some self-imposed) on the divinatory powers she does have. This is really kind of cool; there's not a whole lot of the Mary Sue sensation when reading these books. Tarvik, the Barbarian Warlord Son is a wildly appealing mix of hunky muscle, foodie, romantic -- and utterly boneheaded when it comes to problem solving. It's always hard to know when an author did something on purpose and when it was some combination of blind luck, projection of unconscious desires or whatever. However it happened, Claire and Tarvik together make an unbelievably effective team, limited primarily by their ability and willingness to communicate and negotiate: a very nice fantasy trope that maps well to real life relationships. While a lot of plot development relies on them (especially Claire) NOT communicating and/or being in denial, it never (at least to me) feels like that unwillingness to communicate is plot driven. I _really believe_ that Claire is just being Claire.
I'm partway into Book 4 and am already feeling just a little sad that after that, only 1 book remains (for now?). May Matthews live long and prosper and continue to produce more in this series.
If found Mudflat when I got pissy about the big publishers and the agency model and wanted to know whether e-only publications could Satisfy My Reading Desires. To that end, I found an organization giving e-publishing awards (Eppies) and shopped the list of nominees and winners. The 2nd in this series was a nominee and I'm oh-so-happy that I started with the first book.