The Compleat Angler
(The Contemplative Man’s Recreation: Being a Discourse of Rivers, Fishponds, Fish and Fishing Not Unworthy the Perusal of Most Anglers)
Walton spent most of his energy on his lives of the poets, but is best known for this work on the joys of fishing. The image above is of an early edition. Read for free online at Internet Archive.
This book is the Main Edition.