1. A computer-implemented method of providing information about content of an electronic book (ebook) that is currently displayed at a client device, comprising: receiving, from the client device, an ebook identifier identifying the ebook that is currently displayed at the client device; determining, using the ebook identifier, an ebook-specific set of layers available for use with the ebook responsive to stored book layer data indicating layers that are available for the ebook, one or more layers of the ebook-specific set of layers providing one or more types of information associated with one or more types of ebook content at one or more positions in the ebook; transmitting, to the client device, an ebook-specific list identifying the ebook-specific set of layers, the client device using the ebook-specific list to: identify activated ebook content activated by the user and a position range of the activated ebook content; determine, from the identified ebook-specific set of layers, one or more available layers that can be used to interact with the activated ebook content according to a type of the activated ebook content; and request the user to select at least one layer from the determined one or more available layers; receiving, from the client device, the position range and identification of the at least one selected layer; identifying layer information associated with the ebook content identified by the received position range, the layer information identified specific to the identification of the at least one selected layer; and transmitting, to the client device, the identified layer information for display in conjunction with the activated ebook content identified by the received position range.