Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Good source for looking cantonese characters

I've only used this book to lookup/review Cantonese characters, and it is very good for that. However, the author really should include some simplified characters now that Hong Kong & Macau have been returned to China. Also, if you have internet access, online dictionaries will a better job (more characters, more romanization methods...) plus provide verbal pronunciation.