too many to count, for some reason I kept all of the books I was required to buy for my degree
(including the bloody king james bible)... plus as a kid my mum would buy me all sorts of Enid Blyton, AA Milne, general kids' classics (Charlotte's Web, Roald Dahl collection, Series of Unfortunate Events, HP obviously, the Philip Pullman series, those Artemis Fowl books, and the Horowitz ones about that spy I can't remember the name of)
but I generally try and buy one a month to keep me entertained... last ones I got were Stephen Fry's latest autobiography, and the Rules of Attraction