There's a long history in comics of using anthropomorphic animals to tell adult stories. Even people who have only passing acquaintance with the form know Art Speigelman's Maus, telling the story of his father's experience during the Holocaust using cats, mice and rabbits. Before that, Stan Sakai's Usagi Yojimbo was telling the stories of a bodyguard in Edo-period Japan who happened to be a rabbit; and before that, Robert Crumb's Fritz the Cat was freaking out squares with sexually explicit adventures in the underground comics of the 1960s.

Which is to say that there's pedigree (no pun intended) for Howard Hardiman's decision to turn the cast of his exhaustively researched series about a young male escort, The Lengths, into dogs.

That said, the characters in the book are more anthropomorphised than most of the examples above. Although they have canine heads, except for their claw-like fingernails and the occasional piebald skin, the rest of their bodies are largely human. That's probably for the best, given the amount of sex between the covers (no pun intended, again).

The Lengths examines the double life of Eddie, a young art-school graduate who half-falls, half-dives into life as a male escort. To his friends, he's a young man getting out of one serious relationship and into another; but to the people he meets through dating sites, classifieds and smartphone apps, he's "Ford" (as in, Escort – a pun only he seems to find funny), suffering an identy crisis while finding himself slowly more attracted to Nelson, the beefcake bodybuilder who got him into this world in the first place.

Despite Eddie's stress, the book is no preachy condemnation of sex work. Most of the drama comes not from meeting strangers in hotel rooms for drugged-up orgies (something which Eddie rapidly becomes so comfortable with that he is soon admonished by another escort: "Did you really have to check Twitter while you were pissing on the client? . . . I'm not sure it was the kind of abuse he was after"), but from his desire to keep that aspect of himself separate from his "real" life. That said, apart from some machinations involving two phones, one work and one personal, at times it seems his heart isn't really in it. After all, he lives in a London not of physical brothels (although an early, failed visit to one presents the book's darkest look at sex work), but of Grindr. How is his work any different?

That the tales of life as an escort ring so true is testament to the research that Hardiman carried out. Interviews with sex workers provided the factual background to the series, but the insight they gave him is fully rendered into fiction; there are no talking heads reading verbatim. Everything is presented through the eyes of Eddie, and the story doesn't take a backseat to the desire to impart knowledge.

Surprisingly, aside from aesthetics, the decision to cast the characters as dogs doesn't have a huge effect. The city is so recognisably our own, and the characters so true-to-life, that the distancing which you might expect to come from reading about people who are, literally, not quite human never quite arrives. And the times when it is a negative are rare, although two men with dog faces french-kissing will never look right.

The main benefits of Hardiman's decision are subtler. While it may not soften the emotional impact, it certainly removes some of the erotic charge of the book, and takes the edges off the most explicit scenes – which, it should be noted, are never that visually explicit. And there's no doubt that the various breeds of dog render the characters immediately visually distinct in a way some comics (particularly black and white ones, which don't have hair colour to fall back on) find troublesome.

In fact, there's a far bolder decision than dog heads in the book. Beyond the first of the eight chapters, Hardiman dispenses with two of the most important pieces of a cartoonist's toolkit: speech bubbles and captions. The vast majority of the book is presented with the text just floating near the characters, without even a line to indicate the speaker.

Usually, this works fine; the placement is clear enough, or there is enough context to work out who is saying what. But sometimes, the ambiguity is too strong. It only gets worse when Eddie's thoughts enter the picture. Occasionally, this produces a pleasing double meaning; but just as often, it leads to confusion.

The Lengths is an important work. It covers topics largely passed over even in prose literature, let alone the diversity-challenged world of comics. In giving a voice to the voiceless, Hardiman deserves praise - and behind the anthropology, the Lengths is a love story sweetly told. By the end, I wanted to see its leads together. And that's really all that needs to be said.

The complete The Lengths can be bought from the artist [2], £20.