Have you ever came up with a book idea while totally devoted to one your already

[K-Sweet]

writing? This idea for a book kepts popping into my head

There's a girl named Sophia Rose Ryan. In her world people are bonded with an animal at birth usually the baby of the parents animal. Hers is a White wolf named Lucien ( lou- sha- en ). The people are also born with special powers. Not all are born with them. Even though she doesn't know it she is the second most powerful of her kind. One day a coven of powerful people killed two of the most powerful leaders. The government began killing off the people with powers and bonded animals. On her seventh birthday she had a vision that her family was next to be taken out. She was the only one to survive. Eight years later she meets Nicholas Rolland ( suggest a better name ). His boned animal is a bengal tiger named Dollya. One of his powers is fire along with earth,water( that includes ice), and wind.

I'm fully devoted to the Mourning Sun series, but if this is any good i'll write it after I finish my series.

 

[Look what I can do...]

After writing and during filming of "ET the extraterrestrial," Steven Speilberg wanted to add to the ending by having an Earthling travel back with ET. He saved that idea and wrote "Close encounters of the third kind."
Hey get twice the payoff for two books.

 

[Tulip]

It's perfectly fine if you want to write about two stories at once.
By the way, your idea sounds a lot like The Golden Compass by Phillip Pullman. I'd suggest making it more original. Sorry.