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Is this Ivan's book? and Is this book Ivan's? are (pretty much) identical in their meaning; the difference would be of stress:

Это книга Ивана = This book belongs to Ivan (with stress on whose...

это can be a demonstrative pronoun in which case it declines or it can be a particle (частица) in which case it's undeclinable; the latter translates as "this is" or "these are"

это новая книга =...