market depth questions

What does market depth tell you? Not very much it seems. For NBS Buyers outweigh Sellers but share is not making any headway. Looking at market depth brackets suggests there are mostly if not all retail buyers & sellers?
I find it perplexing to have some small buyer & sellers sitting there with half a cent between them - with in absolute dollars about $20.00 at stake. IMHO partic as a buyer if half a cent is going to make a differenve you should not be buying? ;-)