Well, I mean, I don't think it gets any better than Excel.
What kind of devices are the users going to be utilizing to access the information and what is this address book used for most of the time? Is it usually accessed within a LAN, or do users need to be able to access it from home as well? How well do you need to protect the information?
As I said, Excel is an excellent choice for storing information that requires many fields. If you want to ease the sharing process, you could create a share folder in Google Drive (or OneDrive, seeing how you are already using Excel), use Sheets (or Excel in OneDrive) to store the information and give your employees read permissions. You would only need to add new employees to the list of users with read permissions, instead of emailing the information to everyone every time there is a little change.