gchess33 wrote:
"... Unless you're playing the Sicilian, then most of the people I play use early deviations."
Perhaps that can be used as a rough guide of how much to read in an opening book. I think that most opening books are something of a compromise between exposition and reference material. The idea is for the reader to decide how much is appropriate to examine. Before buying, it is perhaps worthwhile to think about whether one's interest is primarily exposition or reference. I often suggest going to a publisher's site and trying to find an available sample from a book in order to get an idea about the sort of content that is emphasized.
I wouldnt consider anti-sicilians early deviations.