My book on cocktail piano: http://www.billspianopages.com/cocktail
We’ll look at the basics of chord extension, basic chord substitution, arpeggiated runs, chordal and melodic improvisation and a few other useful tips.
This kind of lounge piano style is, as you might know, pretty closely related to jazz, and uses a lot of jazz piano techniques when it comes to messing around with chords and using different scales like pentatonic and blues for melodic improvisation. In actual fact, working on the cocktail style can be a very good way into jazz, as it uses many of the same techniques but within the context of a much freer and easier tempo: you don’t have the pressure of a solid metronome beat.
My other book: http://www.billspianopages.com/how-to-really
Jazz for beginners playlist: https://goo.gl/NQoxci
Piano for complete beginners playlist: https://goo.gl/5UqKP2