Second hand books I've bought

Of all the second hand gardening books you’ve brought, which have you found most useful ?

I don't think I've bought any second hand books and not many new ones. I  do get bought gardening books though as presents quite regularly - they mustn't think I'm doing it right. My one main principle is to never get rid of organic matter whether it is diseased or full of seeds, it goes on the compost heap - with the exception of white rot infection and horsetail roots which go in the verge opposite and on the road to be crushed respectively. I've never had garden waste collected or a garden fire.

I have just looked in my 'library' and seen one book bought second hand 'save your own seed' by Lawrence D. Hills, 40 pages from 1975. That's far more pages than needed but he does tend to ramble on in his writing. At the end he quotes from a 1558 gardening book: "One acre composted is worth acres 3, at harvest thy barns shall declare it to thee".