First off, I read this book on a recommendation when I asked rasfw for a reading list of steampunk books. I understand why someone chose to include it, but it's not steampunk in the way I understand it, though it does have a Victorian setting. This is magic at work rather than clanking oily, fantastical engines and pseudo-science.
When literary scholar Brendan Doyle accepts an invitation to travel back to Victorian London to hear a lecture by Samuel Taylor Coleridge he grabs opportunity even though he barely understands the principles of the time travel jump from one window of opportunity to another. He's been researching the life of minor poet William Ashbless and hopes to fill ion some of the details while he's there. When he's attacked and misses his return window, he's cut loose in the London of 1810 and seemingly in danger from separate sources. If the dark magician doesn't get him, someone else will, either the hunters from his own time or the beggar-lord, Horrobin the Clown, or Dog-Face Joe, the werewolf, who has the ability to leap from body to body when the one he's in becomes too hairy or in dire danger.
Briefly befriended by Jackie, the beggar boy from the rival beggar court, (a young woman disguised as a beggar in order to revenge herself on Dog Face Joe, but Doyle doesn't twig why Jackie is so effeminate until she tells him at the end) he manages to get his bearings and learns, to his surprise, that there are worse things than begging for a living. He tries to make contact with Ashbless and fails, but then after a run-in with Dog-Face Joe finds himself in another body - a younger, stronger, altogether hairier body. When he shaves his face he finds himself looking at Ashbless in the mirror.
But the newer, stronger body is hardly going to save Doyle when he's up against not only Doctor Romany, but also Romanelli and Amenophis Fikee, all magician-servants of The Master who is attempting to destroy British political rule in Egypt and open Anubis' gate into the underworld to let the old Egyptian gods return to the world.
Ranging from the London of 1810 back to the London of the 1600s and then Egypt before ending up back in early nineteenth century London where Doyle is reunited with Jackie for the climax of the book. Doyle is often the victim, but somehow manages to land on his feet, not always due to his own ingenuity.
I'm not sure this always lives up to my expectations or the quotes on the book jacket. It flaggs a little in the latter part of the Egyptian section and the defeat of the Master seems to be a bit of an anticlimax, though he was the originator of the whole gate plot. Horribin the clown and Doctor Romany always seem much more fearsome and more immediately dangerous, and so they are the final opponents to be vanquished.