Peter H.M. Brooks wrote:

I'm curious as to why rye bread is sold cut into very thin slices in
packets. Other bread is sold in loaves and variations on loaves.

Is this just an historical accident or is there some reason for it?

I think it's because a little of that type of rye (rye built from
sourdough, a natural yeast culture) goes a long way.

Is it as easy to cook loaves of rye bread at home, or is there some
difficulty with it?

If you have experience in sourdough bread-making it's not incredibly
difficult to make a decent loaf of straight rye, although it will take
some practice and may taste very different from the slices sold in
packets.

Is it possible to make lighter rye bread than the fairly dense stuff you
find in the packets?

There are several baking/bread-specific groups that could advise you in
detail; the pumperknickel police patrol rec.food.baking :-), so
alt.bread.recipes is a good place to start. I make some lightish ryes,
including a deli onion rye and a deli 'pumperknickel' (in quotes because
it's not a true sourdough.

By their nature straight rye breads are heavier than the equivalent
wheat bread. To cut a long story short, rye doesn't contain the type of
gluten that makes wheat flour rise, and it also contains gums that
interfere with the action of its gluten-equivalent. Lighter ryes are
made by adding a proportion of wheat flour to the rye; the more wheat,
the lighter the texture of the bread (assuming the baker's skill is a
constant).

regards
sarah

--
Think of it as evolution in action.