Q: Crashes when I try and buy a photobook

Repair the library according to the instructions in this Apple document, Repair Your Library, and try ordering again.

Note: If you use iCloud Photo Library with Photos, this action will cause Photos to upload all your pictures again (from Fix missing or incorrect thumbnails in Photos - Apple Support).

Addendum:  I recommend you upgrade your Mac to the latest El Capitan which includes Photos 1.2.  Both have many improvements which, IMO, make the upgrade very worthwhile.

is basic functionality of the software, no?

Before upgrading try the following: launch Photos with the Option key held down and create a new, test library.  Import some photos, create a book and try to purchase and select a shipping address to see if the same problem persists. Does it?  You an always quite the purchase process if you're able to select a shipping address.

is it something to do with my address book or something?

It should be.  The next upgrade to El Capitan is 10.11.2 which includes Photos 1.3 so give it a try.