The blueprint-liquid-grid only includes the rules for the grid layout.
and it's meant to be added over top of +blueprint: You still need to
apply the other parts that are in +blueprint.
You should do this:
@import compass/utilities.sass
@import blueprint.sass
@import blueprint/modules/liquid.sass
+blueprint
+blueprint-liquid-grid
There are no duplicate rules, because +blueprint-grid doesn't actually
output any CSS until you use it as +container, which liquid redefines.
You can also pick and choose modules this way if you prefer, these are
all the parts which +blueprint wraps up:
+blueprint-typography(!body_selector)
+blueprint-utilities
+blueprint-liquid-grid // <= changed from default!
+blueprint-debug
+blueprint-interaction
+blueprint-form
Andrew