Your old sketchbook was one of my favourites. Great to see you've started a new one. Your sculpts are instantly recognizable.
Im a always impressed of how your heads seem to be so alive/have character. Even the obviously "rough" low res ones. I guess ill try to mimic one of your busts to figure out all those nice shapes. I allready sculpted the eyes of one of your sculpts for practise once from your previous sketchbook.
There is one thing i noticed though (not really a critic, more an observation). The expression you use for almost all your busts is very similair. Frown (vertical creases with hollow above eyebrow and one horizontal on the nose) and a slightly unhappy mouth. Id love to see you make some sculpts that explore some radically different expressions.