Read cover to cover, a book of essays gives you the person behind it: their voice, the trend of their thinking, their tastes and the nature of their engagement with the world. So, here are two, one from each end of the human spectrum. Think of Milton’s Archangel Raphael, intellectually wide-ranging, lucid, informative and fair, and you have Francis Spufford. Think of his darkly glittering Satan — vivid, passionate, partisan and fatally persuasive — and you have Martin Amis. Read these books together and you have, in essay terms, a Miltonic whole.

These are collections of what might be called ‘pre-loved’ pieces, not originally designed to cohere, so they have been washed and brushed for resale. True Stories is grouped under abstract headings: Cold, Red, Sacred, Technical and Printed. Each section has its own mini introduction, a kind of headnote. Subjects are as diverse as Polar exploration, Babbage’s proto-computer, Soviet economics, God, Kipling, science fiction and boffins.

The writing, as well as the thinking, is imaginative and sprightly. Roland Huntford, Captain Scott’s biographer, is a biographical rottweiler biting down on Edwardian pieties. Polar ice is frozen time. Consumerism is the magic porridge pot, the lake of stew. Counterfactuals raise the ghosts of other possibilities ‘in order to investigate the groundwork of the real’.

There is just so much to think about here, and Spufford loves to think — dining, as he describes it, on the various aspects of a thought, ‘guzzling its ramifications, digesting it gourmand style’. The intellectual energy in this book is, to shift the metaphor, intoxicating. Its drive, compellingly expressed in the introduction, is always towards notional truth: reading facts, as if they were words, for the wider meaning behind, of which they are only a partial expression. What, for instance, does Antarctica mean?

Then when he has read through to the soul of fact, Spufford examines its opposite: story. This of course must be experienced, not read. The whole thing is an exercise in restless imaginative attention, bypassing traditional approaches to find, behind the panoply of the world, a greater, synthetic and animating whole.

Spufford believes in God. Most of the time he leaves you to your own conclusions. Only where he insists, in ‘Sacred’ for instance, on a Christian reading, did I find him disappointingly reductive. I wanted to watch him not knowing; an intellectual Columbus, heading out for some hazy edge-land where disciplines blur and where there may be God or there may be dragons, and where, either way, Truth might finally offer up her soul.

Cut to the netherworld. Enter Milton’s Satan. Enter Death. The Rub of Time is written in the teeth of mortality. Here is Amis, often at his most brilliant, quick, passionate, very funny and up to his eyes in the mess of being human. The essays, covering a 20-year span, are organised under repeated themes with variation. ‘Twin Peaks’, which features Amis’s literary heroes Bellow and Nabokov, returns like a refrain between headings that cover politics, the British royal family, sport, literature and internet Q and A (one of the book’s rare lapses). Its concern is, what will remain? Its structure is strictly heirarchical. Who is number one? Clue: not God.

What can be made of a world, Amis wonders, where there is extreme violence, pornography, gambling, stupidity, a listless flatulence of body and mind and an obesity that is both mental and physical?

Not nothing, is his repeated answer: defiance and humour and literature. His triumphs here are the familiar fallen angels: Ballard in his suburb; Nabokov; Larkin struggling against his inner cold; Updike — all the ‘transgressive’ writers; and Chloe, the gonzo porn star, whose fragile, hard softness is both heartbreaking and unforgettable.

For all their cleverness, these essays are characterised by their emotional engagement. Amis gathers his personal canon around him, as you might pull a cloak tight against the cold and coming dark. He loves his heroes, all the more it seems for their mortality. Repeatedly, he measures their achievements, asserting first Nabokov’s and then Bellow’s pre-eminence. Behind his insistence is the anxiety of its opposite: what if literature isn‘t eternal? And, implicitly, what about me? Please tell me that something of this will last.

If Spufford writes in the certainty of belief, Amis has only the flickering of opinion to go by. Don’t dismiss it. Opinion isn’t fact, and it certainly isn’t Truth, but it has the warmth and changeability of life about it. It is a sort of intellectual heartbeat: evidence that we are alive and thinking and in the world. It is human and there is, underneath all the swagger, a modesty to that.It’s Life that Amis is interested in. His plea, addressed to Time, is: give us just a little more Life, damn you.