When I bought this book from a second hand shop I thought it was a non-fiction account of two people liberating turtles from a zoo but in fact it's a novel written in the form of diary entries from the two main characters.
William is a dissatisfied bookshop assistant and Neaera is a children's author suffering from writer's block. Both of them are lonely and both of them separately become obsesses with the turtles in their local zoo and find themselves meeting to plot to release the turtles back into the ocean.
There then follows a story of planning and uncertainty, of two people discovering themselves and rethinking their relationship with nature. It's a lovely, thoughtful novel and the writing is beautiful, particularly when describing the turtles.
There they were in the golden green murk of their little box of sea, their bedsitter of ocean. One almost expected a meter in the corner of it where they had to put 5p to keep the water circulating. Thousands of miles in their speechless eyes, submarine skies in their flipper wings. No beach of course, no hot sand for the gravid females to crawl up on to, to lay their eggs.
Turtle Diary by Russell Hoban published by Jonathan Cape 1975, republished by Bloomsbury 2000