I started with Prisoner of Azkaban in the HP series. And if I started reading Discworld with Colour of Magic or The Light Fantastic I never would've given it another chance.

I read Moving Pictures first, but wasn't impressed, then Jingo first a few years later and was hooked. Then Men At Arms, then Feet of Clay, Night Watch, Thud!, Fifth Elephant and Snuff...in that order. STILL haven't finished Guards! Guards!, even though I started ages ago.