I picked up the story a long time ago and a lot of it is blurry. I do remember he would absorb "energy" for antiques. One of the character used to charge him money to "look" at the things in his store.
Book Eating Magician. It's almost completely translated now. Edit: at least, the MC goes through a phase where they go to antique stores searching for rare stuff to "eat". There's another one w a similar premise occuring...
Ah, someone beat me to it. I had to do some research because I didn't remember the name. It should be Mystical Journey.
I think its like skoll said and its Book Eating Magician but Way of the Devil almost fits the criteria as well. He absorbs energy from antiques and other types of objects to power his martial arts upgrades.