Scifi novel number one

And so we pour outta doors
Think-alikes, so perfectly cloned
Is it me who wonders or he?
Which am i - this one or the one behind?
Sing happy birth to me - wish we won't turn against you
What a treat to their eyes: look-alikes and ones of a kind
And if i am, how was i done?
Perfect - or end of variety?
What a feast for their pride: feel-alikes, my sisters and i
And so we pour outta gates
Perfect lack of variety!