I remember, as a child, I used to canter through the woods: in my mind, I was a horse. I'd flare my nostrils, paw the ground and dash through the woods jumping logs. It drove my siblings mad. They couldn't bear my endless whinnying and insistence that they stroke my "mane" and feed me apples. I think everyone thought I'd grow out of my obsession, but I didn't. I became obsessed with owning my own pony. I bought endless copies of Pony magazine and wrote letters to their editors about the horse I didn't actually have. Then, if the letters about "Calypso" were printed, I'd cut them out and paste them into my pony scrapbook. I entered the WH Smith Own a Pony competition every year.

I badgered my mother for a pony on a daily basis, saving up every penny to buy it the accoutrements it needed  brand new head collar, grooming kit, hoof oil, saddle and bridle. I read endless horsey novels by the Pullein-Thompson sisters, Ruby Ferguson and KM Peyton, whose 1968 bestseller Fly-By-Night (part of the Roth Hollis series) was my favourite.

Which is why If Wishes Were Horses is the book for me. It is subtitled "a memoir of equine obsession", and in it, Susanna Forrest describes her ongoing fascination with horses with such clarity, such a feel for how horses can affect your life, that she took me right back to a childhood of Thelwell and Follyfoot. Like Forrest, I was desperate to cadge rides from anyone; I rode as and when I could. I once sneaked into a field and leapt on a pony bareback I was so desperate. It immediately bucked me off.

Forrest's grandmother was a saddler's daughter, and she herself rode from when she was tiny, recalling her mother's hand clapping "my fat little leg to the saddle". She describes the predominantly young girl world of caring for a pony, the ritualistic grooming, the plaiting of the mane, the way horses almost become like dolls for the young girls who want to care for them. There is an oddly practical lyricism in her descriptions of this care: "I groomed Tango with the plastic currycomb when he was moulting, turning the air into a snowstorm of gingery tufts of hair, like being caught in a vacuum bag."

Hers is a richly evocative book, describing the smells, the sounds, "the clanking of the fork on the wheelbarrow". There is a chapter called "Gymkhana" that took me right back to the Betjeman poem "Hunter Trials" ("It's awfully bad luck on Diana / Her ponies have swallowed their bits / She fished down their throats with a spanner / And frightened them all into fits")  girls with pigtails flying around on naughty ponies while mothers fussed and bossed.

But Forrest is not only concerned with the childhood love of ponies. Along with her poetic recounting of riding again now she is in her late 20s  booking a private lesson in a riding school in the suburbs of Berlin where she now lives  she has also discovered all sorts of nuggets about horses. For example, we apparently ate horses for 90,000 years until, 5,500 years ago, we decided to ride them. "There is little fat in horse meat  it makes excellent sashimi." Elizabeth I designed for herself a riding skirt to cover her stirrups  women rode side-saddle, of course, and her skirt was covered in black velvet and adorned with pearls  and hunted stags with silver-tipped arrows until her old age.

Forrest visits hunts, talks to the people who run the Pony Club, researches horse rescue centres and goes to endless farms. She does surveys, takes advice on Equus Eroticus ("the community of adult human pony erotic role players") and her pages benefit from hectares of groundwork. This is not just a tale of one woman's love, but of swathes of people who are involved in the equine world.

It is packed full of tales of golden horses, chariots and children riding round the streets of Brixton. And she reports the conversation with a woman from Sydney who describes "the horse that only I could ride". We've all had that experience. Mine was called Roger (yes, really), a fiery chestnut. We stayed together until he was 26. When he died, I held his head and wept and wailed for him.

By middle-age, women often call their horses "my man"; they change to a different type of love object. But love is certainly the appropriate word  Forrest describes a horse she is about to have a lesson on: "She was also beautiful, the glossy black of a lacquer-work cabinet, polished and nourished till the highlights of her coat were white under the barn light." Forrest knows that the connection between rider and horse as you gallop, flying through the air, is almost indescribably strong. Nothing comes near it.