A dehumidifier seems like a good idea, in general. It does use a good
amount of energy (it's something like a smallish refrigerator with its
door always open, running continuously).
Any closed bookcase will eventually match temperature and humidity with
that of its surroundings. However, the closure (of whatever sort) also
keeps out dust, of course, and that's desirable.
As to materials, particle board seems to be popular; I don't like it, but
it is practical (and heavy). Old particle board released small amounts of
formaldehyde from the adhesive that bonds the wood chips, so be cautious
about old particle-board furniture.
HTH, a bit, and good luck!
--
Nicholas Bodley /*|*\ Waltham, Mass. (Not "MA")
When I think of The Blue Marble, I become emotional.
I don't usually feel that way. There is nothing more
dear in all of human experience.