You asked about three books, but allow me to mention 4.
GinA is written by Dierk Koenig, Guillaume Laforge, and Paul King -- all three contributors on the Groovy project (Guillaume is the tech lead). The forth author is Andy Glover -- an expert on
unit testing. It does a nice job of presenting the best parts of the language directly from the mouths of the folks who wrote it. The metaprogramming parts are bit dated now with the release of 1.5 (more on that in a moment), but 85% of the book is still valid. There aren't plans to update this book until Groovy 2.0 comes out (realistically in 2009), so it is what it is for now.
For the most up-to-date, as well as IMHO the most comprehensive coverage of metaprogramming, DSLs, and the like, Venkat's new book Programming Groovy is the one to pick up. Venkat and I started writing Groovy Recipes together, but quickly realized that we were writing two very different (yet complementary) books.
Groovy Recipes is for busy programmers - just the code, ma'am. "How do I parse a RSS feed?" -- here is the code to do it, and here are a couple of paragraphs explaining what is going on. It's still a very readable book, but it is a tactical book whereas Venkat's is a strategic book.
Def Guide/Grails is a very good book -- Graeme Rocher is the author and the tech lead on the Grails project. It, unfortunately, is a bit dated as well. It was written in the 0.3 days, and Grails 1.0 just came out this month. There are plans afoot to upgrade it to 1.0, but you probably won't see that edition until Q4 of this year. The good news is the book is still more right than wrong. It's still the best place to take a deep dive into the technology. There is a new book coming out soon -- Practical Grails Projects -- that might hold you off in the short term until DGG ships.