Cornelia Funke's The Thief Lord is my favourite of all of her books which I have read (I confess I've not got hold of a copy of Inkspell the sequel to Inkheart yet as I didn't much enjoy the first book.)
Two orphaned boys are hiding out in Venice, having run away from their aunt who wants to send 12 year old Prosper away to a boarding school, and to take custody of 5 year old Boniface (Bo to everyone). At the start of the tale the two boys have travelled from their grandfather's home in Hamburg to Venice, the magical city about which they heard so much from their mother who died three months previously. When they arrived in Venice they were befriended by a gang of four children: Riccio, who is a pickpocket; Mosca, who loves boats; Hornet, who loves books and whose real name is Caterina; and Scipio, who is the eponymous Thief Lord. Unfortunately for Prosper and Bo, their Aunt Esther has tracked them down to Venice and she employs a tortoise-loving detective named Victor Getz to locate them. Fortunately Victor is too sympathetic towards the boys to be a villain, and he gets entangled in the adventures of the gang, and ends up helping Bo and Prosper instead of handing them over to Esther and her horrible husband.
Things I like about this book include Victor's vanity: he's so absorbed in admiring his reflection of himself with his new fake walrus moustache that he doesn't even hear the Hartliebs coming up the stairs, and he assumes they're admiring his "handsome" nameplate when they don't immediately knock on his door; and Hornet's passion for books.
I have to confess that I wondered all over again, just why Max and Esther Hartlieb even want to adopt Bo, given their clear dislike of children (Max Hartlieb complains that they are "fidgety and loud, and often quite dirty", and have "no idea what's really important" !)
I must also confess that I was quite convinced, on my first reading, that Prosper would also use the magical roundabout to age himself just a few years so that he could become Bo's legal guardian.
I did a quick Google search to discover who was "the book man" (ie. Nicolo Tommaseo, whose statue is a meeting place in the book). It turns out he was a 19th century Dalmatian scholar who fought against Austrian domination in 1848. Annoyingly I couldn't find a photo of his statue that actually shows the books !