Q. What's the best way to care for a leather-bound Bible?
A. The conventional answer is to use it, the theory being that oils from your hands will keep the leather supple as the Bible ages. This theory has the dual advantage of sounding pious and requiring no additional effort on the part of the reader. That's been my own approach, and it seems to work. I don't apply leather care products or observe any special care regimens, and so far none of my Bibles appears to have suffered from the neglect.
Having said that, I've heard from readers who've gotten good results using a variety of leather products -- sometimes to preserve the cover, sometimes to improve it. If you use the Google search in the sidebar, you can hunt up some of the recommendations. Better yet, I'd like to invite readers who've used leather treatments successfully to post about them here. If you do, please include a link to where the product can be obtained, if you have one.
A word to the unrealistic: no elixir is likely to transform bad, cheap leather into a luxuriant pleasure for eye and hand. The money you could spend in chasing that chimera would be better invested in a quality cover!
J Mark Bertrand