Are you looking for recommendations?
Anything by Dr David Hessayon, Alan Tichmarsh has written books
-I would suggest a visit to the charity shop-you will be spoilt for choice
i love Alan Titchmarsh gardening books as I dont find them intimidating. Some books make me feel like I am child playing at being a gardener!
Dr David Hessayon books are fantastic, I picked up the flower expert for a £1 a couple of months ago. I know I will be using this book for years.
I also have his house plant expert (so did my mother) follow his advice & you can't go far wrong.
Many of my gardening books I buy from a charity shop in town. Terrific value for money as some of my books cost £39 new but bought them for £3 or £4. They always have Hessayon books in too.
I don't think you'll find one book that will do it all in sufficient detail. I have the RHS Encyclopedia as well as their Dictionary of Plants and Flowers, which is my favourite book for ornamental plants, But for the edibles I turn most often to the Hessayon "Vegetables and Herb Expert" and "Fruit Expert", which are cheap, reliable and easy to use. I even have a spare copy of the fruit and veg one, which I keep in the shed. I also like the Readers' Digest "Food From Your Garden" which includes sections on preparing and preserving fruit and veg.
Second-hand books are fine but make sure they're relatively modern. Old books won't include the best new plants, varieties and materials, and may recommend the use of chemicals that are now banned and unavailable.