Maik Schmidt is also the author of an earlier book, also from The Pragmatic Programmers, called "Enterprise Integration with Ruby" (I'm calling it EIR for short); yes, I know - the names of both books are similar (see below for more on that). I had written a short review about EIR, here:
after buying the book and reading it.
To summarize, I think it (EIR) is one of the best Ruby books I've read (and also one of the better programming books overall that I've read).
I had a quick look at the contents of this new book, ER3, by Maik. The fact that it is written by him, plus the table of contents, is what makes me think that this book is likely to be quite good too - despite the fact that, going by the table of contents, some of the topics in the two books seem the same (however, it could be that there is more material in the new book on any given topic). But of course, I'll have to actually buy and read it to know for sure.
Here is the full table of contents of the ER3 book. It's a Beta book, so the exact content may change.
UPDATE: I read the full table of contents for the book; it looks like ER3 has quite a few more topics than EIR has. I suspect the format of the book may be a bit different from EIR, too, in that each topic may be shorter (since they use the words "Recipe" in the book title), whereas many or most of the topics in EIR were covered at some length, with the author showing the evolution of improved versions of the software in some cases.
Vasudev Ram - Dancing Bison Enterprises