This 380+ page book combines three volumes into one: A Guide to Thieves' Guilds, Filling in the Blanks, and Into the Wild, all geared towards aiding Referees and characters in venturing out into the wilderness and high-level domain activities.
A Guide to Thieves' Guilds provides guidance on forming and running guilds, both for the PC interested in establishing a guild and for the Referee wanting to add guilds to their campaign.
Filling in the Blanks provides numerous tables and charts that help Referees flesh out hexes for use in hexcrawl and sandbox campaigns.
Into the Wild includes guidance for running hexcrawl campaigns, a random weather generator, rules for establishing and running domains, an abstracted mass combat system, rules for mercantile trading, guidelines for creating BX-style character classes, and some alternate classes for BX games that add a little bit of flair to the originals.