i cant believe i never realised lowyat had forums for readers...

my three would probably become 1000 if i dont stop... but i think when u say three must reads... it depends on the genre... rite? i mean if you are a fan of fantasies... i'd list harry potter right on top of the list... but there are those who are completely against books like that...
so...
for general fiction i'd say:

1. the curious incident of the dog in the night time
2. the catcher in the rye
3. the alchemist
4. a thousand splendid suns

(sorry cant help but list another one... coz i couldnt decide which to reject from the list)