Just get ref from the internet and Draw draw draw..It's all just lines at the end of the day.. the more you do the more they make sense and you can manipulate them to do what you want.. You should keep this book. A new sketch Book would show a lack of confidence in your old work IMO. Nothing wrong with changing style and subject in a sketchbook.. That's what it's all about. I personally love seeing the progression people make through their sklechbooks. Just look at Bumskee's book on here to see what is truly possible with hard work.
Dont give in..Keep posting! :-)