I am writing a YA series. The first story is in my final editing and I am working on the second with ideas for #3. I plan to query in a few months after final touches to #1 mss.
I decided #1 is urban fantasy / paranormal romance. There are hints that some people are not from our world in the first book, but it all takes place in a very ordinary town. At the end of the book, the main character is taken to another world. I don't get into space travel or aliens (much) in #2, but it isn't our world and the story takes place in a city with a castle and royalty... more of a sci-fi / epic fantasy with still that paranormal romance as another main story line. .
I know people like to know what they are getting into when they start a book. Do you think this shift of genre within a series is a marketing failure waiting to happen? I couldn't find many examples of a series that change like that. Would that immediately turn you off as an agent?
Remember I don't work in YA much. And I really don't work in urban fantasy/paranormal romance.
I will tell you that one of the great truisms of writing a synopsis is to make sure aliens don't suddenly arrive in chapter 14.
While yours don't, they do arrive in the next book.
The question you want to ask yourself here is whether readers who love urban fantasy and paranormal romance are going to love the story in Book #2. Does it have the elements of the kinds of stories your readers like? In other words, will they go along with you for the ride?
And let's just all remember that it takes the dragons awhile to arrive in Game of Thrones.
And Sookie Stackhouse got much darker as the books progressed.
Write the book you want to write. See where it takes you. Readers will follow a good story.