Acers are deciduous, so they normally begin to lose their leaves at this time of year. Not easy to tell until Spring if the plant is dead or just resting.

Owdboggy's right, but hopefully you kept the tree well watered since planting - if its a large Acer such as Acer griseum, rather than Acer palmatum, it would have needed a couple of gallons of water a week...

Also it might depend where you planted it and if there is a prevailing wind which will have "burned" the leaves and made it look as though it is dying. If so - it will recover next year but be prepared for a repeat performance....acers do not like windy positions where they dry out fast too.