The Hobbit/Lord of the Rings/Farmer Giles of Ham*/Anything else Tolkien wrote, Wizard of Earthsea, The Chronicles of Pern, all David Eddings books, The Chronicles of Thomas Covenant Unbeliever, The Book of the New Sun, War of the Worlds, Narnia, Hitchikers Guide to the Galaxy (but I was and am more a fan of the radio series, which I had on cassette), Harry Potter (I was, when I started reading them, exactly the same age as Harry Potter, considering I was bought The Philosphers Stone for my 11th birthday), and a lot of old-school stuff: I have a complete collection of Biggles books, and I used to love Hornblower, as well as Robert Louis Stevenson, Enid Blyton and Just William when I was younger and other more 'grown up' adventure novels (I am confident in saying I am the biggest, if not the only, John Buchan fan on this forum). On the opposite, my family also has a mind-numbing collection of 50's and 60's boys adventure annuals collected by my Uncle and father, so I also read large amounts of things like Victor and Eagle. Fuck those things are amazing. You couldn't get away with even thinking about publishing shit like that now. The WW2 stories were the best: all the Germans were called either Fritz or Hans and spent most of their time killing innocent people, shouting 'GOTT UNT HIMMEL' or being stabbed and shot by commandos in funny wooly hats. All the Japanese people were an absolutely virulent, mind-numbing yellow, had huge teeth and even less personalities. When I was 13 I was completely addicted to Lord Peter Whimsey mysteries and Sherlock Holmes. I was also quite big on over-romanticised Victorian/Edwardian historical novels like Hereward the Wake (who is, according to family mythology, one of my ancestors), the whole of The Once and Future King (and Le Morte d'Arthur come to think of it), Ivanhoe, etc.
I think my most concrete reading memory must be the Hobbit though. I was 6, and my parents had the tape of the BBC radio adaptation in the car on a long journey. The music completely enchanted me, and I got in to the story quite a bit, but the real reason I actually read the book was because I fell asleep at one point and missed the start of the bit where Bilbo meets Gollum, and as such could not work out what the fucking hell was going on. So I read it and the rest is history.
*Seriously, has anyone else in the world ever actually read this?