The great thing about learning from a book is they pick tunes for you that are easy to play on the instrument. However, once you get past the basics you need to decide which style you really like, and what you want to use the instrument for.
We did a ' carols and folk song' night recently and I put in a morris set to remind people of summer, and I was pleased to see most of the audience had smiles on thier faces and were tapping thier feet.
I like to use the box when leading the band in dance sets for dancing, or to accompany song in a noisey pub where my other acoustic intruments would not be heard. I'm not a great fan of massed melodeon, except in a workshop or outside for the morris, and I remember it took me a while to learn the technique of playing quietly so not to drown out the flutes and whistles.
Enjoy it all
FloraG