I'm currently reading Eclipse 3 Live, by Bill Dudney, which was reviewed on Javaranch
here.
I'm pretty impressed so far. One of the better things it the publisher's (SourceBeat) model of delivery - rather than getting a paper book you get a year-long license to download a PDF of the book. The author, in turn, agrees to update the book with new information over a year or more. So it's less likely to be out-of-date.
In particular I've found with Eclipse that any books on the shelves are already out of date. Although this is true of almost any printed IT book, Eclipse seems to have a particularly fast release cycle, with major features coming in pretty fast.
I'd strongly recommend this book. It pointed me straight to features that I'd taken months to find just by using Eclipse itself. There's a sample chapter out there too (linked from the article) if you're interested.
--Tim
(Disclaimer: I've been given a free 3-month subscription to the book to give feedback)