I don't know about 'Little Green Book' But Harrington is ... the point is that early stage tourney, when stacks are large and blinds small play pretty much like a cash game (at least if you are a tight conservative player like Dan H), so yes HOH is good for cashgames

Middle of HOH vol 2 you get to later stage theory and when to push all in with any trash and such .. that off course only relates to tourneys