The Loose Association of Wargamers

I'm going to look at it slightly differently, supposing a devastating flood wiped out all my books & PDF's what are the first three books I would replace?
Neil Thomas: Ancient & Medieval Wargaming. That way I could get a game with most of my historical stuff
Henry Hyde: A Wargaming Compendium. Stop sniggering at the back, we did our damnedest to break the rules over a few games and they still held together. They would work even better if people showed a little self restraint. Besides, there's a host of other good stuff in it.
Rick Priestley: Warmaster Historical set (A bit of a fiddle rolling 3 into one)

No nostalgia selection that gets read and never applied. If you only get three you need three that you will use.

If on a island alone, the one book I would bring is,

Engelstein, building blocks of tabletop game design.

With that a pad, a pen and your reference material you can create whatever you feel like.

To my selection above, I'd also like to add Prebble's Culloden.

Longer term you need all the classics, pretty much every generic book on wargaming should be bought, there aren't that many.

More rare works should include F.E Perry's first and second books, good finding the first! You need an origional Little Wars (signed) and Featherstones entire catalogue (signed). Also a copy of Charge (signed & immaculate)

Agree with Buff on the Neil Thomas' Medieval book! I'd need a copy of AGW too.

Ian Heath’s WRG books would be high on my list - Armies of the Middle Ages 1&2, Armies of Feudal Europe
Then CS Grant - Scenarios for Wargames and Programmed Scenarios for Wargames
Tony Bath - Setting Up a Wargames Campaign

In terms of pure history:
Sumption’s 100 Years War
Runciman - History of the Crusades
Norwich - The Norman’s in Sicily
Duffy’s - The ‘45
Captain J C Dunn - The War the Infantry Knew
Haldane - The Insurrection in Mesopotamia 1920
Alistair Horne’s - To Lose a Battle: France 1940

At least, they are the ones I grab if the house caught fire!

Dunn was a hard one to leave off my list I admit.

Black Powder
Hail Caesar
Black Powder II
Warlocks of Antietam

You teaser you.

I'd give different answers for nostalgia versus now. Nostalgia?
Battle - C. Grant
Ancient Wargaming Airfix Guide - P. Barker
Setting up a Wargames Campaign - T. Bath
Honourable mentions, Funcken.. CS Grant, Hyde, Featherstone

Now.. too many outside of actual rules sets. Actual rules sets? Hmm.. TFL oeuvre as a sneaky single choice, DBA, and as a 'one set to rule them all from 1700 - 1890 - Horse Foot & Guns. It's surprisingly good at what it does. Honourable mentions to the 'Rampant' & 'xxxx Commander' series. Good fun games all, no rivet counters, no accountancy, and a minimum of markers.

I don't own a single 'generic' book on wargaming. I've had a flick through them on trade-stands, but they've never floated my boat and I've then gone and bought a history book or set of rules instead (although the line does often get blurred between 'rules' and 'books about wargaming which include rules').