River Monsters: A Tale of Obsession, Adventure, and Very Big Fish. Available from bookshops in the UK (most bookshops will order for next day).
Or you can order signed copies from Icon Films (River Monsters production company) https://www.rivermonsters.tv/product-page/river-monsters-book-by-jeremy-wade
The US version, River Monsters: True Stories of the Ones that Didn’t Get Away is available now
Audio book available here: https://audiobookstore.com/audiobooks/river-monsters.aspx
There are also editions in the following languages: Bulgarian, German, Hungarian.
Somewhere Down The Crazy River (with Paul Boote 1990)
This book is out of print, although second-hand copies (hardback and paperback) can sometimes be found.