I use ruby for simple tasks and because I find it fascinating. Ruby is 
the only computer language I "know".

In my experience, a combination of at least 2 books is essential. Often, 
I understand something only when I get a look at it from a different angle.

The combination I recommend is:

The pickaxe book ("Programming Ruby", Fowler) and
"Ruby by example" (K.C. Baird).

In addition, I have "The Ruby Way" (H. Fulton) and "Ruby Cookbook" 
(Carlson & Richardson).  They are also useful.

Cheers, Jöòg

Thanks for the answers. I decided by Ruby.

What is the best book Ruby for someone who does not have experience in 
programming?

.Learn To Program
.Why's (Poignant) Guide to Ruby
.Humble Little Ruby Book