''Down the Kitchen Sink'' has much in common with its famous predecessor, ''Down the Garden Path'', in which Beverley Nichols described his early forays into the realm of gardening. When he began to write the first, he could not prune a rose. When he began to write the second, he could not boil an egg. Perhaps this is why both books remain fresh and eminently readable. The phrase 'kitchen sink' may suggest squalor and disillusionment, but Beverley Nichols transforms it into a symbol of merriment and adventure. With a new foreword by Roy Dicks and Val Biro's charming drawings, the Timber Press edition of ''Down the Kitchen Sink'' deservedly takes its place among Beverley's classics on gardens, homes, cats, and other friends.