Re-reading a favourite book is like visiting a friend, says Pete Kelley.

It's one of the tests of good writing, I guess, that it repays a second, third or 27th read… and that's especially true when you come back to a novel at different times in your life. I've written a lot, over the last couple of years, about the privileges of retirement… and done so, I hope, not to make those still working feel bad, but to encourage those who've hit the 'Big R' to value the positives.

We're all 'on a journey' these days. It seems obligatory. So this month - as a change from banging on about the pleasures of volunteering - I wanted to mention the journey I'm on through my own book shelves.

If you like books at all, then over the decades you collect them, sift through, chuck some out, buy some more… and by your 50s you've got a shelf or five full of ones you really appreciate. Some are old friends. But they're not friends you know as well as they deserve.

Henry Thoreau's On Walden's Pond, for me… the original bible of self-sufficiency. Or wise and thoughtful George Eliot's Middlemarch. Vassily Grossman's epic Life and Fate, an astonishing novel describing the Second World War defence of Stalingrad.

In non-fiction, try my 'Desert Island' book, Peter Watson's The Modern Mind … a soaring rollercoaster ride through all the big ideas of the 20th century.

But right now I'm all at sea with Herman Melville's Moby-Dick… an adventurous ripping yarn about a young man on an early 19th-century whaling ship, rich in detail.

I'd read it before, but missed so much. And one little fact leapt out at me this time which had completely passed me by.

Whales tend to live in pods - family groups of 10 or 15, perhaps. We all know that from documentaries. But by 1851, when Melville was writing, whaling had reached an industrial scale. Many nations were hunting them.

And Melville tells us these astonishing creatures had started adapting … travelling in large 'convoys' of up to several hundred. It made them harder to find (when there was no better technology to locate them than a sailor watching from the masthead). And was also for protection.

He describes an encounter with one of these convoys. As the whaling ship approached, they formed a circle… and placed the 'women and children' on the inside.

Melville wrote long before conservation concerns. He seems to mention this just as a curiosity. I don't know about you, but I find it heart-rending.