"I am writing in this book."

Translation: Ebbe a könyvbe írok.

[RO_4_PM]

Does the use of the illative imply an action taking place?

ebben a könyvben írok - i (do) write in this book

ebbe a könyvbe írok - i am writing in this book (right now)

[Findil]

"Ebben a könyvben írok" would mean that I am somehow in the book and I'm writing there. But you could say "Ebben a könyvben arról olvastam, ..." -- "In this book I read about..."

"Ebbe a könyvbe írok" is literally "I write into this book". Your words "move into" the book.

Basically, when talking about writing, use "ebbe a könyvbe" and never "ebben a könyvben".

[vvsey]

Just a little note. You could talk about what the author has (already) written in the book.

"In this book he writes/talks about his life."

"Ebben a könyvben az életéről ír."

But, again, this is something that has already been written in the book. The author is "in the book". Literaturally.

[Zsuzsi97194]

A questin about word order, again. So if the focus is which book then the word order is correct here. But if the focus is that I am writing and the particular book is incidental then would it be correct to use "írok ebbe a könyvbe?