Decline in books on Ruby

I’ve noticed, at least from my searching on Amazon (where I primarily
purchase materials) what appears to be a decline in the number of books
and reference materials on Ruby.

Years ago, I bought the Learning R. book from ORA. It was riddled
with errors, but I liked its very basic introduction. Since then, ORA
hasn’t produced much – this book hasn’t been updated, nor do they
respond to inquiries of such.

So my question is, am I the only one noticing this decline. If it’s
real, I wonder what the driving factors are. For example, decline in
usage of the language, not finding good authors (or they prefer to write
technical materials for what they feel is more marketable languages),

Thoughts, opinions, etc. welcomed. Thanks!

“The Well Grounded Rubyist”:

The second edition was published in 2014. I
think this is one of the best ruby books. It’s
a beginning to intermediate book.

“Programming Ruby 1.9 & 2” (known as the Pickaxe)

Updated in 2013. For me, the Pickaxe was sort of
a must have beginning book because of the docs
in the back of the book where I could look up
methods and scribble notes.

“Ruby in a Day”

Came out in 2013. A new entry in the field.

“Beginning Ruby:…”

(Peter C., 2009). I thought this was a very good
beginner’s book. Needs an update.

“The Ruby Way”

New edition coming out in 2014. I thought this was
a good book, however I think of it as more of a
reference book.

“Metaprogramming Ruby”

Just came out with a new edition in 2014. An excellent
intermediate to advanced book.