World Coin Books

Start with Krause - World Coins for a start - it is set up by century and used editions are cheap - just make sure you get the last edition and not a 20 year old one. New they are expensive.

Then when you decide what you want to collect get the best references for the particular series there is.

Always buy the book before the coin to prevent getting ripped off.

Depends how far back you want to go back in World coins.
If it is only four centuries Krause is by far and away the best bet, because of the illustrations.

My World collection goes right back to the invention coinage, and covers all cultures.
So I have a lot of reference books, too numerous to mention here.
If you want a book that covers a period or culture that is more than 400 years old, there is a possibility that I may have some sort of reference.

Just ask for a particular culture or period, and I will post what I have for my reference. I will tell you what I think of it.