Test whether a list contains a specific value in Clojure

Question

What is the best way to test whether a list contains a given value in Clojure?

In particular, the behaviour of contains? is currently confusing me:

Answer 1

The problem with the 'recommended' solution is it is breaks when the value you are seeking is 'nil'. I prefer this solution:

(defn member?
  "I'm still amazed that Clojure does not provide a simple member function.
   Returns true if `item` is a member of `series`, else nil."
  [item series]
  (and (some #(= item %) series) true))