On page 41 you write
cond has no default fallthrough expression,
I first thought, that the conditions must be exhaustive (as e.g. in Rust for the match expression or with the new case-statement in Java), but this is not the case in Clojure, so one could say that the default fallthrough expression is nil.
I propose to add a note bevore the above sentence, that cond returns nil is no condition is found which evaluates to true.
The simplest example to demonstrate this would be
user=> (cond)
nil