I've used bookcases in the past, quite successfully. If the bookcase is a solid wooden one, make sure that it has not been painted with lead paint. You'll have to make holes in a solid wooden back for drainage. If it's an inexpensive bookcase made of laminate with some sort of thin backing, you can put holes in the backing or just knock it off. If you have burrowing animals in your area, replacing the backing with hardware cloth or chicken wire might be helpful, but if you don't have critters of that sort, don't bother. Putting down cardboard to act as a grass/weed barrier is helpful, or you can remove the sod and put it in your compost pile before you install the bed.

thanks for the feedback demeter.
i feel foolish asking, but how would one know if there are burrowing critters around (i've just moved in)? i was thinking i'd just knock-off the back of the case, lay it down on an area that's pretty devoid of grass/weeds. use a mix of new potting soil, free fill dirt from the neighborhood & some of the yard-made compost -- should i buy/add some steer-manure/fertilizer?

is it better to use a barrier (atleast newspaper/cardboard that'd break down & potentially benefit the soil) or use nothing between the ground and the soil of the raised bed?

should i be starting this process now, or would that be very untimely & i'd better wait until the tail-end of winter?

There are plenty of things you can start now; check your county extension agent web page, or call them. I'm sure they could tell you what to plant when.

If you choose to wait till spring, you could always fill the bed now and plant a cover crop of winter rye and/or fava beans or the like. Turn them under a few weeks before you're ready to plant in spring, and your bed will be that much better come planting time.