While I respect the Californian reader's suggestion that potential buyers also consider two other slang dictionaries, I point out that Green's work goes far beyond only American usages. There's plenty here about English, New Zealand, Canadian, Australian, and other variants of English.
Nice touch: the editor's introduction comes complete with an e-mail address. Any reader who finds a usage that Jonathon Green doesn't know about, is free to send it in for future editions. But I personally find few usages that Jonathon Green doesn't know about.
Excellent work but, because of attention paid to "rude words", probably not a good gift for children.