blue book vs booklet

blue book and booklet both are nouns.

Word	Noun	Adjective	Verb	Adverb
blue book	Yes	No	No	No
booklet	Yes	No	No	No

As nouns, booklet is a hypernym of blue book; that is, booklet is a word with a broader meaning than blue book:

Other hypernyms of blue book include brochure, folder, leaflet, pamphlet.

blue book (noun)	booklet (noun)
a register of persons who are socially prominent	a small book usually having a paper cover
a report published by the British government; bound in blue
a blue booklet used in universities for writing examinations