To buy books without consulting at least some review or comment on them is probably a bad idea. Amazon.com has proven that simply compiling reviews and marketing books based on them, and on product affinity, is very effective (they were one of the few dotcoms to actually survive the bust).
Consumerium Services can obviously and easily support lookup of reviews and other commentary on a book by ISBN-barcode. There is potential for a worn device, possibly with other software that already exists for price comparison, to provide an alternative buying option. This would not be good for the retail location, but all that Consumerium could do about it would be to make integration easier or harder.
A friendly retail location can be convinced to support Consumerium Service access onsite to look up related books that the reader might enjoy - boosting sales. Making price comparison harder might be part of that deal.
Additional value is added by faction participation, as the reviews can be filtered according to who one trusts in general on buying decisions, not just who one trusts "about books". The whole basis for book buying advice may well be factionally defined and have nothing in common from faction to faction.