In my life, I've learned and used the following languages, in this order: Logo, Basic, Pascal, C++, Java, Python, Ruby, Clojure. Each time that I learned the next language, I thought it was a great improvement on the previous, and I wondered what I had been spending my life doing with the previous language.
My experience is that with Clojure is a testament to pretty much everything in "Beating the Averages" (http://www.paulgraham.com/avg.html) It's hard to know for sure, but I have a feeling that I will end up using Clojure far much longer than the rest of those languages, combined.
If you are contemplating learning a language for one-off commands and sysadmin scripts, then I kind of prefer Ruby over Python and Perl for expressiveness and readability. Most Rubyists are of the Rails persuasion, but I still have never learned Rails.
I came to Lisp via "The Little Schemer", and I recommend it for people who are new to Lisp (and/or programming). It's short and sweet, but explores some really interesting and deep ideas (recursion, higher order functions, the Y combinator, the halting problem, and interpreters). I like to think of it as "SICP lite".
It won't teach you Clojure, but it will open your eyes and set you on a path to Clojure, and I think give you a very strong grounding for Lisp. At least that's what I think it gave me.
On the other hand, if you really want to get up to speed on Clojure specifically, Rich Hickey's talk "Clojure for Java programmers" is a great intro to the language. I don't think you need Java experience to get something out of it, it's mostly targeted at non-Lispers without much functional programming experience.
If you can wait til Apr 22 (by Amazon's release dates), there will be 2 more clojure books which I'm pretty confident will be excellent, in addition to 2 Manning books which are also great.
By 'nothing' I mean that I'm a sysadmin, knows a smattering of PERL, a little BASH, a lot of this and that over the years.