Along the Saltwise Sea

I'd say this is suffering from middle book syndrome, except I just found out there are four books in this series, fourth scheduled to come out this year, and for all I know, that isn't the last! 
I'm afraid unlike Seanan McGuire's Wayward Children series (author name shown is a pseudonym) this doesn't read as a universe with self contained stories, but a continuation of a main narrative, which can make the installments frustrating even when they're not particularly cliffhanger endings. 
I do still enjoy the adventure, the fanciful world building, the clear-eyed nudging both young and adult readers towards compassion and emotional intelligence via the character-building experiences of the protagonists, rather than simple moralizing.
I think it will be easier to continue in the series now that I know the format each will take.