How old are you? How old do you want to be? If you had the chance would you choose to be older? Would you choose to grow old at all?

If only that were an option. Spanish cartoonist Paco Roca's quietly sad graphic novel Wrinkles - published in Spain in 2007 but only now making its British debut - is a book about ageing, about being elderly and "the thousand natural shocks / that flesh is heir to".

It's not an experience we like to think about much, is it? As Roca himself has said: "We can empathise with lives that aren't our own. We can empathise with a Roman emperor or a psychopath, but there are so few times that we can empathise with an older person."

Wrinkles, calmly, cleanly, painfully, forces us to face how we treat people in their twilight years, the damage caused on brain and body by ageing and the wounds inflicted by a society that no longer has a place for them.

It's the story of Ernest. Once a banker, he's now suffering from the early stages of Alzheimer's (though he doesn't know it). His son can't cope with him and is keen to get him into a retirement home and effectively wash his hands: "We are very busy with our work and the rest ... I don't think we can come very often."

In the retirement home Ernest shares a room with Emile who is mentally sound, a thief and a cynic. "There's nothing in this home," he tells Ernest at one point. "At eight o'clock, it's breakfast. At noon, we lunch and at seven o'clock, we dine. The medication and the food are our only motivators."

Not everyone is so sceptical. Adrienne needs a frame to walk but she enjoys the exercise classes and the bingo. Mrs Rose sits at the window and happily imagines she's travelling on the Orient Express to Istanbul. Georgette lovingly looks after Marcel who also suffers from Alzheimer's but is too far gone to know he has it.

But all of them are living lives restricted by their ageing bodies. Some are raging against the dying of the light and some are on the verge of winking out. What matters is that, as Roca's story reminds us, our humanity doesn't have an age limit.

There are deep currents here. At first you might not realise because of the quietness of the telling and the sereneness of the art. Roca's lines are characterful but never showy. The surface is so still it looks and feels glassy. But if you dive in you will cut yourself.

It is also technically adroit. The transitions between past and present, experience and fantasy are beautifully handled by Roca, yet another example of the way in which the comic form slips through time more easily than any other.

Wrinkles is, inevitably, a bleak story. There is no happy ending with Alzheimer's. But then does life ever have a happy ending? But this is also funny and alive and in the middle there is one page - one memory - that is as potent a vision of love's possibilities as anything you'll read this month.

What is this then? A light in the darkness perhaps.

Wrinkles, by Paco Roca is published by Knockabout, priced £12.99