Four Strings are so fundamentally different in complexity of play from a guitar - I could never have imagined!
With this book I soon understood how to form chords and use them on the whole length of the fretboard.
There are some things that really take time:
1 - learn the notes on the fretboard on every of the four strings
2 - use them as a base to form major, minor and seventh chords
3 - learn the different scales
4 - now you can add whatever solo melodies and chords you like in that key to songs AND play with other musicians EASILY!