The first Hewitt book
https://www.amazon.com/Hunted-Zodiac-Murders-Revised-Serial/dp/0990857573/ref=sr\_1\_1?dchild=1&keywords=hewitt+zodiac&qid=1621193576&sr=8-1
https://www.amazon.com/Hunted-Zodiac-Murders-Revised-Serial/dp/0990857573/ref=tmm_pap_swatch_0?_encoding=UTF8&qid=1597225008&sr=8-1
The first Hewitt book is possibly the most accurate retelling of the case with a wealth of detail.