telephone directory vs phone book

telephone directory and phone book both are nouns.

Word	Noun	Adjective	Verb	Adverb
telephone directory	Yes	No	No	No
phone book	Yes	No	No	No

As nouns, telephone directory and phone book are synonyms defined as:

telephone directory and phone book: a directory containing an alphabetical list of telephone subscribers and their telephone numbers

Other synonyms of telephone directory include phonebook, telephone book.

telephone directory (noun)	phone book (noun)
a directory containing an alphabetical list of telephone subscribers and their telephone numbers	a directory containing an alphabetical list of telephone subscribers and their telephone numbers