Book Series Question

[Nik]

Denise wrote: "The first book is a crime mystery novel. The second book is the conclusion of the first book, yet it's transformed into an action book with some mystery as to what's going to happen with character's from the first book...."

I think crime mystery and action with some mystery are compatible genres. Thriller - romance or fantasy - non - fic transformation might be less digestible.
It's hard to predict the receipt by the public and thus to decide what should work better, but maybe a feedback from beta-readers would clarify a little how each option is perceived?
Best of luck, Denise, with series or standalones! -:)

[Quantum]

Denise wrote: " If a reader is expecting a crime mystery in the second book, they will be disappointed."

I think you kind of answered your own question and I'd tend to agree with you, even though the genres have some similarities.

It's hard choice.

Option 1
Readers can grow to like a series and it's more efficient for you as a writer. In order to accomplish that here, you'd have to create another major mystery to be solved in book 2 and excise the action (to be used in another book, perhaps).

Option 2
Or maybe you're thinking that the 2nd one could be the beginning of a second series. One idea that popped into my head is to create new characters in book 2 yet maintain the existing plot and story universe. Maybe those new characters know the ones from book 1; maybe they live in the same town or work in the same police department/law enforcement agency; maybe they left the police dept and have their own PI company.

In the end, I think it's a matter of what you're motivated to write about b/c then you'll be willing to do the work. ^_^