I agree on the novel Treasure Island by Robert Louis Stevenson, a great book with so many memorable scenes- the old pirate at the Admiral Benbow Inn, the black spot, Long John Silver as the friendly cook, the boy hiding with the apples etc etc.
I like his other novels as well, Dr Jekyll and Mister Hyde (it would be great to read it not knowing the story in advance), and the Scots dialect novels Kidnapped and Catriona.
A lot of the Treasure Island films are pretty boring, I can't remember which ones I have seen. I did note that Oliver Reed is in one, playing Billy Bones.
No wonder, I don't remember Oliver Reed, as he appeared in the version with Charlton Heston as Silver. I think one of the few film versions I have never seen. It might be worthwhile for me to see if I can find it and watch it, as it also stars Christian Bale as Jim, Christopher Lee as Pew, Richard Johnson as the squire, Julian Glover as the doctor, and Peter Postlethwaite as Merry.