I haven't done any Java programming since SE 6. Would your book be an appropriate refresher? Also, I have it in my head that learning C would make me a better Java programmer. Is this reasonable or ridiculous?
If you feel like you're past the beginner's stage of Java, a lot of the book would cover the same ground, but there's one notable exception: Closures are a killer new feature you wouldn't have learned about in Java 6. Programmers have been asking for this feature for a long time.
I am writing another book to come out later this year that gets further into advanced topics, Sams Teach Yourself Java in 21 Days. As for others, I like what Bruce Eckel does in Thinking in Java and I'm a huge fan of Elliotte Rusty Harold, but I'm not aware of either doing a new book specifically for Java 8. Harold's Java Network Programming came out last fall and is sitting on my desk begging to be read.