Character Analysis
The Man with the Magic Voice
Mo's pretty unique because of his ability to read characters and objects out of books. Meggie thinks at one point that "Nobody else in the world had a voice like her father's. Mo could paint pictures in the empty air with his voice alone" (1.52). Super cool, right? Except Mo never reads in front of his daughter, because he's frightened that he'll read her into a book and never see her again, or he'll read something out of the book that'll harm her. Yikes.
What's up with the nickname Silvertongue, you might be asking? Consider this story Mo tells about when the first time he summoned Capricorn, Basta, and Dustfinger out of Inkheart. Dustfinger pled for his life and "cowered in awe in front of me—a magician, he thought, who seemed to know all about him and who had plucked him out of his world as easily as picking an apple off a tree" (16.16). And Mo kind of is a magician, since he can pull characters out of books and into the real world (and vice versa) just by reading aloud, hence the name Silvertongue.
It's also worth mentioning that Mo professionally repairs books, which is itself like magic. For instance, Meggie has seen him restore some particularly damaged books in the past. Check it out:
Meggie knew what really old books looked like. She had seen books in Mo's workshop with their pages spotted like leopard skin and almost as yellow. She remembered one with a binding that had been attacked by woodworms. The traces of their jaws had looked like tiny bullet holes, and Mo had gotten out of his book block, carefully fixed the pages back together, then, as he put it, gave them a new dress. Such a dress could be made of leather or linen, it might be plain, or Mo might imprint a pattern with his tiny decorative stamps. (5.15)
Yep, it sounds like Mo's so skilled when it comes to saving books that he's got near-magical powers. And though he has the potential to read someone super dangerous out of a book and into the real world, when it comes to fixing books, Mo just creates beauty.
Father of the Year
Mo obviously really cares about his daughter. His first thought is usually how to keep her safe—which ain't easy when you've got a power-mad villain like Capricorn running around. For instance, when Basta and his men first come to fetch Mo and the book at Elinor's place, Mo tells them to leave Meggie alone, yelling:
No! […] My daughter stays here or I won't give you the book! (6.68)
We're not sure that's he's actually in a position to bargain with these bad dudes, but the fact that he tries shows us what his priorities are. And at the top of the priority list, time and again, sits Meggie—as Elinor says, "I don't know any father who's more besotted with his daughter than yours" (8.15). So just like Meggie thinks the world of her only parent, so too does Mo think the world of his only child.
Although we never meet any of Mo's side of the family, we know that "Both he and Meggie's mother had large families whose homes, so far as Meggie could see, were scattered over half of Europe" (2.12). So we're left kinda curious about what sort of upbringing Mo had that turned him into (a) such a huge bookworm, and (b) such a caring dad.
Mr. Shifty
On the emotional front, Mo's kinda multifaceted. He's a softie in general, inclined to giving people the benefit of the doubt. So much so, in fact, that he realizes that when he brought Dustfinger over into this world, "It broke Dustfinger's heart" (16.26)—and Mo feels bad about it. This is pretty impressive considering how much havoc Dustfinger's wreaked on Mo's life.
Even though Mo promised not to mention Dustfinger when talking to Inkheart's author, Fenoglio, he soon breaks that promise, saying, "Very well […] I'll tell you. But Dustfinger will murder me if he finds out" (24.51). So yeah—we're not going to entrust Mo with our secrets anytime soon. We don't think he's bad intentioned, per say, but he is definitely self-serving.
In addition to Mo being a nice (if somewhat dishonest) guy, he's pretty easy to read. Here's what Dustfinger thinks of him: "Silvertongue's face always showed his feelings; he was an open book, which any stranger could read" (26.7). It's kinda funny for Dustfinger to characterize Mo as an open book, given that what Mo does professionally is open up books and then fix them… and that it's only because Mo opened Inkheart that Dustfinger's in this world at all. Maybe Mo is more like the things he loves than he admits to himself.