This book was published in 1981 and has been out of print for a long time. Used prices are anywhere from $29 (what I paid, luckily) to $215!
In 2007, I scanned one of my copies and created a nicely-formatted PDF version. Andrew Lynch and I were in the process of obtaining permission from Mr. Ciarcia to release it for free due to the rising used-copy costs, but things never progressed to where the file could be released.
It’s taken two years, but everything has finally been worked out! As described in this Circuit Cellar newsletter note, Build Your Own Z80 Computer is now available online on Google Books or as a downloadable PDF.
The downloadable PDF is my work.