So apparently this is National Pet Month, and I've surprised myself and somehow acquired a pet of my own. This is Little Bear. He arrived yesterday, with good timing: today I turn 25, which seems a good time to embark on a new beginning.

There's a long tradition of writers and their animals, though I don't know if any famous historical author was moved to write about a hamster. But Elizabeth Barrett Browning had her spaniel Flush, Virginia Woolf had her dog Pinka, and Lord Byron kept Bruin with him at university, and walked it around the courts of Cambridge on a lead (which all makes sense, except that Bruin was a tame bear). The famously macho Ernest Hemingway actually lived in a house full of cats, and Charles Dickens kept a raven and taught it to speak and perform 'comic turns'. I've never been quite sure how I feel about pets. As Virginia Woolf once wrote: ‘We deliberately transplant a little bit of simple wild life, and make it grow up beside ours, which is neither simple nor wild’. The whole process of 'buying' an animal, of 'owning' it, seems to me a strange one in a lot of ways - and I think there's a risk that even a well-loved animal becomes suffocated by its doting, anthropomorphising owner. It's only a few species of animals that seem to thrive in captivity, and I've never been sure that hamsters are one of them. This pet, however, was a bit different, since it was abandoned at a local rescue shelter. I saw the pictures of the small animals by chance, after looking with a friend at rescue dogs, and felt unexpectedly sorry for them too - they are often, apparently, abandoned with far more casualness and cruelty than the larger pets.

Kiran Desai wrote about the injustices we casually deal out towards animals in The Inheritance of Loss; this is the old, embittered judge speaking about his beloved Mutt: 'A man wasn't equal to an animal, not one particle of him. Human life was stinking, corrupt, and meanwhile there were beautiful creatures who lived with delicacy on the earth without doing anyone any harm... The world had failed Mutt. It had failed beauty; it had failed grace.' On the one hand, in the middle of the great injustices in which the judge and his family find themselves entangled, this lamenting over a pet might appear comical, even obscene. But on the other hand, I'm not sure the animal's sufferings themselves are a thing to be treated lightly. We humans are self-important creatures. We look at our own lives with grandeur, and think of other creatures as somehow different in kind, less real - 'it's only an animal'. To treat an animal like a human, to talk to it in baby-language and hand-feed it chicken as the judge does, is clearly slightly ridiculous (Mutt probably finds it rather laughable too) - but to respect an animal like a human seems to me just.

I couldn't really take a dog from the rescue centre - I don't know where I'll be living in two years, or five, and I don't think a long-lived pet would appreciate being constantly uprooted. But a hamster was possible, and so I ended up with Little Bear. I didn't want to shut him up in a tiny cage, so I've made him a natural habitat. It's surprisingly rewarding to watch him learning to burrow, to climb, to dig in sand - something I don't think he had ever seen before. While I've been working on my book, he has also been busy in his tank in the corner of my office, constructing an elaborate tunnel and nest system. He's also built a toilet, a food hoard and a hill, and - for some reason best known to himself - buried an entire plant. Watching him crawl about organising his home, it's clear that his concerns, to him, are no less important than mine are to me. Which gives every life on this earth, and every labour, a certain kind of perspective. And that isn't a bad insight to come to on your 25th birthday...

I'm just back from London, where I had a meeting with my agent, Simon, to discuss my new book. Good news - he likes it! More than that, he was pretty excited about the whole project. He instantly understood what I was trying to achieve, and was keen to read the rest. So I thought I'd share the news, which is a massive relief after months of working on this book.

As well as praise, my agent had some excellent suggestions. He has a great gift for seeing a project as a whole and winnowing out what is most important from what is extraneous or stilted, more 'scaffolding' than real writing. So the book is going to have a new title (there was always a choice of two, and Simon could see more clearly than I could which was the natural one). It is going to remain in the third person, rather than shifting into first person as I had thought it might. It is also - thanks to a particularly brilliant and rather high-concept idea which I can't claim any credit for - going to have a different structure, one which really pulls together the various threads of the narrative. The book (like many early drafts, by writers both new and seasoned) had a rather awkward prologue that wasn't doing much except sitting there slightly pompously at the start of each section, clearing its throat. Instead of this, it's going to have something more exciting and immediate, truer to the real story at the heart of it all.

I got back to my desk with a clear sense of the path I need to follow in order to get the rest of this story finished. It's a story which I believe in passionately, and which I want to tell in the best possible way, and it has now received an enormous boost and vote of confidence. I'll be working hard over the next few months to keep the momentum going and by autumn, with a few more meetings and discussions along the way, I hope to have a completed draft. At that point I'll be able to share much more information about the book - but for now, I can tell you that it's a historical story which follows a single family over 100 years in Europe, from the First World War up to the present moment.

I'm often asked whether a writer needs an agent. You can write without one, of course - and all writers write at least their first book this way - but I don't know if you can sustain a career without one. Writing is by its nature a solitary, long-term and precarious occupation. A book can become a black hole which subsumes other elements of your life - the more so the more passionate you are about the idea that you want to bring to life. For instance, I gave up another job to work on this book. I also took the decision to write the whole thing before submitting it to my publishers - something authors routinely do when they make a significant leap in genre or style or take a creative risk, but which nevertheless means that I'm essentially working on it uncontracted. Which is why a good agent makes all the difference. Simon has discussed ideas with me from the beginning, and generated many of the best ones himself; he has reassured me that the book is worth working on, that it will find an audience; and he has got me out of a lot of creative dead ends and blind alleys along the way. Having support from an agent means that there are two of you who rise and fall on the success or failure of the book, two people invested in its fortunes, two critical sets of eyes for when it isn't working out - and two people to celebrate when it does. If you're in it for the long haul, you're probably going to need an agent alongside you.