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Some books say that the order of adjectives is important where there is more than one adjective in front of a noun. The following should be observed:

Opinion, size, age, shape, colour, origin/nationality, material/purpose + noun.

Would you say:

A long sad Russian novel or

A sad long Russian novel. Why?

The adjectives expressing opinion seem to be rather confusing to me.
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the order as I know it is as follows:

1) DETERMINER.........A

2) OBSERVATION........GORGEOUS

3) PHYSICAL DESCRIPTION

a) size..........LITTLE
b) shape..........OVAL
c) age............NEW
d) colour..........BLACK

4) ORIGIN............SWEDISH

5) MATERIAL..........LACE

6) QUALIFIER.............STRAPLESS

7) NOUN.............BRA
Comments  
I think we generally avoid using more than 2 adjectives before a noun (unless they're of the same type e.g. 3 colours). There's no rule about this, it just sounds a bit strange to have a lot of adjectives before a noun. If we need more, we usually make two sentences (at least when we speak). Think that natives don't usually study the rule of order of adjectives, it comes with practice.
In your example, IMO the second one is correct ' a sad long Russian novel'. 'Sad' is an opinion - what is sad for you may not be so for someone else. But both sentences sound a bit stilted.
What do the others think?
 chris's reply was promoted to an answer.