Hi relitively new to fishing (2 years) bought many books but i think i have missed the should haves. a top ten must have books would be an interesting question.

Depends on what you are fishing for. give us a clue Salmon,Seatrout.trout or Saltwater.

would it be Halford, Skues etc?

The practical angler; or The art of trout-fishing more particularly applied to clear water

North-country flies. Comprising eleven plates of hand-painted illustrations, from the author's own drawings, with particulars of the dressings and season of each fly; and chapters on fishing the minnow, the creeper, the stonefly, and the worm in clea

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WHEN YOU LEAVE THE RIVER, TAKE NOTHING, AND LEAVE ONLY FOOTPRINT'S!!!

THA CAN TELL A YORKSHIREMAN ,BUT THA CAN'T TELL HIM MUCH !!

Just 10 thats a bit cruel.
Anything by, Yates, Aston, Bucknall, Skues, Halford, Ritz, Lawton, Headley, Parton, Falkus, Sandison, Bailey, Gathercole, Lapsley, BB, Geirach, Pennel, Mcguane, Williamson, Dawson, Roberts, Walton.........

ABSOLUTELY NOTHING by Wilson

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It depends what you are looking for. Do you want to be taught stuff or to read something nice?

I have gathered more from this book than from any other:

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Is this for a collection, for reading enjoyment or to glean some info.?

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As stated above you need to be a little more specific.
Are you in intersted in trout, salmon, game in general, fly-tying, instructional, informative, collectability or elegance of prose?
I believe one of the main magazines has started asking leading angling contributors to list their top 6 favourite books recently which may help. I am also sure if you look through earlier topics in this section their will be threads along the line of what you are seeking

I find instructional books a bit tedious so the books I like are of wild experiences. To that end my favourite books are:

A Singing Reel by Moray MacLaren. It's about fishing in Scotland, Shetland (they don't regard themselves as Scots!) and the Faroes. The best book about fishing I have read.

Fishing in Wild Places by David Street. Fishing Mainly in Ireland and Scotland. Wonderful.

Going Fishing by Negley Farson: One of the best known fishing/travelling books and an excellent read.

mainly a good read but a little education comes in handy!