By the same reasoning, no book on Java can be any good. Take the set of books about java, and let n be the cardinality of this set. For any book about Java, call it B, there are n-1 books that are not B. What would be the meaning of having n-1 books out there, if B were any good?
As it turns out, the Sun tutorials are an excellent starting place, and they're probably one of the main reasons why Java is such a popular language. When Java was introduced, it came with excellent documentation from the beginning. The popularity of Java, particularly as a teaching language, is what led to the massive number of books about the language, as writers realized that there was a huge market. So the vast number of introduction-to-Java books is in fact a direct consequence of the fact that the original is so excellent.