By far #1 book recommended on Gratitude. No one explains it better than Rhonda Byrne- An Earth Angel in deed! The Magic by Rhonda Byrne.
“The evidence of gratitude’s power working is always that first and foremost it makes you happy. The secondary evidence of gratitude’s power is that you attract wonderful things. And as if that wasn’t enough, the happiness you feel after practising gratitude also attracts more wonderful things, which will make you even happier.” Rhonda Byrne
Easy To Follow Video Course on Gratitude-Attract Abundance through Gratitude. Walks you from Day 1 to Day 21