It's always fun to have someone to play a piano duet with, be it a sibling, a parent or child, a teacher or another pupil, or friend. Besides it being fun, it is a great way to improve one's sight reading ability, as there is someone else playing with you to keep you going. Also, it teaches unison playing, both hands in treble, both hands in bass, antiphonal singing/playing, modulation, syncopation, hemiola accompaniment, changing time-signatures, echo singing/playing, dissonance, chromaticism, resolution and more. Indeed, this book is a great tool as it contains well-loved Christian songs and is therefore great as a gift or Christmas gift.