Another nice kit from Dave. For the novice, bear in mind that ruins always require a good deal more cutting than intact building models.
For 15mm (or smaller) I'd recommend just affixing the two sides to cardstock and foregoing the 'tops' and 'bottoms' of the walls, you'll save a huge amount of fiddly cutting and the difference will be barely noticeable once you've blacklined the tops of the cardstock. (You can do this in 25mm too if you really want, it won't look quite as nice, but it does save quite a bit of work.)
In 25mm, for those walls having a separate top section, be sure to glue the top section to one side wall first, then do final assembly. It's much easier than sticking the sides together first and dropping the top in.
Even more than most paper models, these really scream out to be affixed to a base of some sort.
[4 of 5 Stars!]