Phone book apps (especially German ones, given the name "Telefonbuch") are subject to strict GDPR and data privacy laws, which often keep such archives off public marketplaces.
If you are looking for a for iOS, popular and verified options include: Das Telefonbuch : The official German directory app. Truecaller : A global caller ID and directory service. monument2-telefonbuch-ipa
If this is a bespoke "monument" project meant to digitize old phone books for a museum or archive, it would not have public "reviews" in the way a commercial app does. Phone book apps (especially German ones, given the
It may be a file hosted on a private or niche repository (like GitHub or a corporate server) for an internal tool used by a company or institution. Why no formal reviews exist: If this is a bespoke "monument" project meant