Programming Clojure is a great introductory book but it is a bit out of date now since it deals with Clojure 1.1 and a lot of new things were added in Clojure 1.2.
Clojure in Action covers Clojure 1.2 and takes a very practical, pragmatic approach to teaching Clojure and showing how to solve real-world problems. I'm enjoying the MEAP immensely.
The Joy of Clojure is also worth looking at because it focuses on the "why" of functional programming - but it has a very fast ramp up so it's not necessarily an ideal "first book" on Clojure (but I'd heartily recommend it after you've read Clojure in Action!).
There's also Practical Clojure which is a solid introductory book on Clojure (but several reviewers have said it's not as "practical" as its title suggests).
I've only read CiA and tJoC so I can't comment in depth on the other two but I wouldn't want to be without either of the two I have as they teach completely different things (the "what" / "how" in CiA and the "why" in tJoC which really gets your mind into Clojure idioms).