What Is The Difference Between The Red And Blue Book.

Both books provide very basic prices, one for retail and one for dealer pricss (blue, as stated above).

But they are ONLY guides. Most common coins are priced too high in many areas.

I only have the Red Book.
20% dealer margin seems to be very slim to my way of thinking, unless there is a good dealer prospect of immediate turnover.
I am a price cherry picker, and strictly a collector,
but I look for more like a 50 % margin, although I don't always achieve that. (Sometimes achieve much better)

I do however, look for bargains across the whole of numismatics, not just U.S. coins. The much wider numismatic horizon makes it far easier to find coins for my collection at opportunistic prices. Decades of experience helps.

I would agree with that.
The collectors work out the prices between themselves.
The dealers just adjust their pricing strategy to suit.

Overall, a more honest and open marketplace.

Just remember that since either comes out yearly, they couldn't possibly know what the present market is. Just a couple of outdated guides.