At the top of p.1 he states that "there are no other axioms" than associativity; at the bottom he states that "groups are semigroups" even though they have two other axioms. This type of terminology makes monoids be semigroups, and groups be monoids, and all of them be groupoids. This is like a physician identitying him- or herself as a highschool graduate, or Gen. McArthur as a graduate of West Point.
On page 4 line 13 he states "the reader will make sure that ...", and on page 5 line 2 from the bottom he states "the reader will happily verity that ..." - very, very peculiar verbiage for a math book which should be teaching not just listing tasks for "the reader".
On page 33, the term 'regular' is stated but its definition is hidden in the following Lemma - a peculiar mixture of definition and implications.
Reviewer: Retired Prof.