Should I finish this book and start a new one or start one and try to do both?

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Me and Mateo
Fanfiction*please read* mature readers only may contain drinking cursing and sexual intercourse descriptions kaylanni just moved from her father's house in California to her mother's house in Michigan because of her anger problems. Problems that led her to...
Well...?
Should I finish this book and start a new one or start one and try to do both?