Title: The Contemporary Eruv: Eruvin In Modern Metropolitan Areas
Author: Yosef Bechhofer
Price: FREE
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From Amazon Reviews:

This book is an excellent mix of both practical halacha and the sources and development of that halacha. Having built an Eruv for my community starting with this book, I can tell you that I was NEVER surprised at the rulings of the supervising rabbi on questionable parts, nor was I ever unprepared for any question on why & how I handled problems.

The best English book on eruvin.
This is, without a doubt, the best single halakhic book written about eruvin in…