Loads already mentioned here.
I was looking at my copy of Moonfleet at the weekend. It has my mother's handwriting in it, saying, "Weymouth Book Fair 1977."
Weymouth Book Fair featured quite a bit in my childhood. When I was about 11 or 13, my best friend and I were allowed time off school to be taken down to Weymouth to see Anne Digby, and as a result, most of my copies of Trebizon are signed (not all, as she was still writing them.)
I think I may have seen Rosemary Manning there, too. We certainly had a copy of Dragon in the Harbour, which I think was set in Weymouth. Those books were the reason I insisted on going to Kynance Cove when I went to Cornwall. And where I learnt the word widdershins.
I was very keen on Blyton - the Faraway Tree, Secret Seven, Famous Five, Five Find-Outers, St Clare's and anything else which came my way.
Catherine Storr - Clever Polly and the Stupid Wolf.
Narnia.
Hobbit then LotR.
Asterix.
Tintin.
Chalet School, Abbey School, Angela Brazil. Fith Form at St Dominics, Jennings.
Laura Ingalls Wilder.
Diana Wynne Jones, especially Chrestomanci.
Pony books - Monica Edwards, Jill, Jackie, Jinny, anything Pullein-Thompson.
Silver Brumby (I went to the Snowy Mountains when I went to Australia because of these. Saw wild brickies, but no silver ones.)
Lorna Hill's ballet books.
Margaret Mahy, especially the Changeover.
Rumer Godden - the Greengage Summer
John Christopher- Tripods trilogy.
Douglas Adams - Hitchikers Guide to the Galaxy
Susan Cooper - Dark is Rising series.
KM Peyton, especially Ruth Hollis/Pennington/Jonathan Meredith, but I've read almost all of hers.
Biggles (rereading some currently.)
Nancy Drew
Hardy Boys
Three Investigators
Doctor Doolittle
Animals of Farthing Wood
Elizabeth Enright's Melendy series, as introduced to me by the school librarian.
Hornblower.
I have 8 Mary Plain books, bought at a jumble sale in my cousins' village.
Swallows & Amazons.
We didn't have a TV till I was 14, so I read everything.