I've been reading this one lately, it's not so much practical typography, but rather the history and backstories of types. I find it quite a fun read, and it can inspire your interests and appreciation for types, if you don't already know much about typography.

http://www.amazon.com/Just-My-Type-About-Fonts/dp/1592407463

Butterick's Practical Typography[1] is free online and a really good read.

To go beyond just one book there are good posts and book recommendations on Typekit Practice[2].

[1]:http://practicaltypography.com/

[2]:http://practice.typekit.com/

I’m not sure if there’s a better book out there for UI design in general, but The Elements of Typographic Style[1] was the typography bible.

[1] http://www.amazon.com/Elements-Typographic-Style-Robert-Brin...