The obvoius answers for beginners, bound to come up at some point, are:
Nancy Childress' recent book "Class field theory", Springer
David Cox's "Primes on the form $x^2+ny^2$", Wiley (I think)
Besides these the notes by Milne mentioned in the comments above are really excellent, as is the approach by Neukirch (as is given in his book "Algebraic Number Theory") even though this is rather abstract.