On page 26 you explain the use of anonymous functions with the example
(require '[clojure.string :as str])
(filter indexable-word? (str/split "A fine day it is" #"\W+"))
-> ("fine" "day")
You explain the invocation of split with “The call to split breaks the sentence into words, …”.
Probably you could mention that with #"\W+" a regular expression is defined (which will probably be explained later in the book).