I feel like the topic particle would fit nicely with 특히 in stressing that this book in paticular is especially interesting.
I agree, reported 1/22/18.
책은 is grammatically correct, because it's an object, right?
(1) Yes. 책 is an "object" in the sense of being a "noun".
But in this sentence, it is not an "object complement" (usually marked by 를/을).
(2) re. That book
그 책이 = The book there (identification)
그 책은 = The book referred to (categorization)