My son picked this because of the garden title and garden part of the
story and sent it for my birthday:

The Garden of Evening Mists by Tan Twan Eng.

ISBN 978 1 78211 0187

The Japanese-garden aspect is one part of a wonderful story; I raved
about it for weeks so J bought me the same author's other book for
Christmas (The Gift of Rain) which is nothing to do with gardening but
just as gripping.

http://www.amazon.co.uk/Tan-Twan-Eng/e/B001JP1BFS

Enjoy

Janet.