Hi,
Another single subject book worth considering is
Trout, an Illustrated History by James Prosek.
David Hammond, his wife and I went to a lecture by James Prosek at the Insect-Wine pairing in November. He explained how his interest developed in trout. His first experience was deep sea fishing with his father, which he didn't enjoy. When he was 9, his Mother left the family. Around this time, his best friend took him trout fishing near their home in Connecticut. For whatever reason, he was smitten and fished as often as possible. He fished in areas where it is prohibited. He was caught by the Conservation officer who allowed him to continue and nurtured his interests. At 13, he began corresponding with trout experts to delineate what are the native trout to various rivers and streams. When he was 16 and had a drivers license, then he began driving around the country to hunt the native trout. Once caught, he painted their images and took notes for his edification. At 19 while at Yale, he was submitting a book proposal on the trout book, which was declined numerous times. Knopf took the project because Mr. Knopf himself was a trout fisherman. James Prosek is now in his late twenties and working on his 8th book.
Another interesting book he has authored
Fly-Fishing the 41st: From Connecticut to Mongolia and Home Again : A Fisherman's Odyssey. He traveled the 41st parallel around the world fishing trout. Only when he came upon a dessert did he divert north or south to reach a trout stream.
On another occasion while in England, he had to go to art museums to identify native trout. There had been so much overfishing and stocking of ponds with non-native fish, it often made it impossible to find the native fish due to inbreeding. He was allowed to fish at an estate where records of the lake's activity had been kept for centuries. This lake was unique because it had not been restocked and very likely native fish were present.
I can confidently advise Hammond and I were very impressed by James Prosek. You may want to consider borrowing one of his books from your local library.