English Translation
This book will be of great use to us.
私たちに役立つ sounds unnatural a bit although understandable because 役立つ is usually preceded by an object or event rather than human beings.
この本は私たちの●●にとても役立つだろう。(e.g. 私たちの勉強に)
この本はとても私たちの役に立つだろう。
are more natural collocations.