Nowadays, in the era of everyone having smartphones to look up numbers, actual “big” phone books are a rarity.
And, true, any phone book found in a house would be an obsolete paper weight useful maybe to level an unbalanced piece of furniture and just like the game has it, boring to read.
But, did you know old school phone books had maps of the city you are in?
While some of the businesses would have long since closed (not due to the zombie apocalypse), it would still have a decent map of whatever city. Probably one of the few physical maps in a time when Google Maps is down for good.