In Beaver World is Enos A. Mills's intimate natural history of Castor canadensis, distilled from years of patient vigils beside mountain streams. Chapter by chapter he unfolds the beaver's life cycle, social organization, and architectural craft—dams, lodges, canals—linking each to seasonal rhythms and risk. His prose couples anecdote with measurement and plain exposition, situating the beaver as a keystone engineer whose hydrologic works expand wetlands and diversify habitat. The result is a narrative that anticipates ecosystem ecology while remaining rooted in vivid field scenes and the cadence of early twentieth-century American nature writing. Mills, a Colorado naturalist, guide, and key advocate of Rocky Mountain National Park, wrote from a life embedded in the high country. Managing a lodge and leading expeditions, he kept notebooks on nearby colonies through droughts and winters—experience that grounds his plea to recognize beavers as conservators of water and soil. Scholars of environmental history, field naturalists, and readers curious about nonhuman engineers will find the book instructive and restorative. It is recommended for those engaged in watershed restoration, rewilding, or climate adaptation, and for general readers seeking lucid, humane science writing with enduring practical relevance. Quickie Classics summarizes timeless works with precision, preserving the author's voice and keeping the prose clear, fast, and readable—distilled, never diluted. Enriched Edition extras: Introduction · Synopsis · Historical Context · Brief Analysis · 4 Reflection Q&As · Editorial Footnotes.