What Are The 3 Best

I have never owned a world coin book and I assume you are main,y talking about Australian coins. I think mcdonalds is very good. Halving the catalogue prices gives you a close approximation of what you should be paying. Renniks values are closer to actual but still too high and aren't as simple as halving to get approx value. It still has some good info in it though. In 1991 macdonald released a book titled Collecting and Investing In Australian Coins and Banknotes. Although it is a bit old and some newer information is available, much of the information contained within is very helpful. These are the three Australian books I would buy and I don't think there is too many others out there really.
Before you buy them have you checked the library. I have not purchased a new catalogue for a few years but instead put in a request for the library to buy it and they usually do. Saves some money you can put towards coins.

i was meant to go to the library last week, but I arranged a meeting to buy some coins and forgot all about the library, glad I did as that purchase led me to getting the silver coins. going to try again tomorrow, might try and meet the lady at the library, that way I can get there early and have a look.
couldnt shuffle my budget enough to buy the lot in one go, so paying for more than half tomorrow and the remainder next week, keeps my budget intact that way as well. :) phew he says lol

#1: "Collecting Australian Coins" by Tom Hanley and Bill James. When I was in primary school in the 1970s I borrowed the school library copy of this book for four months straight, until I had read it cover to cover several times. Excellent information about Australian coinage from the Proclamation to the time it was published, just after decimalization. Years later, I found an old surplussed ex-Chinchilla Library copy for sale and snaffled it. The information on pricing is a bit out of date (1930 pennies are only $400) but it's still an excellent read.

My #2 and #3 choices depend on whether you're talking about Australian coins specifically, or coin books in general.

In General

#2: Krause world coin catalogue, 1987 edition. My first Krause, and one of the last editions they made where 1820-present were all in one volume. Best one-stop-shop book for world coins ever. I kept it and still used it even after I bought a new 1900s catalogue in the mid-1990s. I eventually disposed of it after buying a full set of 1601-present volumes in 2006 - much to my regret, because I did not find out until it was too late that the new books had lots of errors and omissions the old one did not have.

#3: Sear's Roman Coins catalogue, the old 3rd edition. Again, an all-in-one-volume work that's almost as good as the multiple-volume, $200 each "millenium edition" you can get nowadays.

Australian coin books

#2: Renniks, 21st edition (2004). The first and so far only edition (that I'm aware of) that included tradesman's tokens. Most useful all-in-one-volume Australian numismatics catalogue, ever. Later editions that omitted the tokens in favour of expanded banknote and NCLT sections simply aren't as useful to me.

#3: "Heads I Win", by Watson, Thomas and Bennett. It tells the story of David Allen Gee, Australia's most notorious coin forger, and some of the brazen con jobs he almost got away with, from the point of view of the police officers that brought him down.

I vote for #3 Heads I win. I am not much of a reader but I couldn't put this book down.

I had coin dreams for months that I was involved in some sort of underworld coin mafia.

1966 book oh how to add in decimals and conversion rates for the decimal currency from pounds. From Australia post and called working with decimals.