Graphic novels are collections of comic books or standalone books as a single book or books with #s. Trade paper backs (TPB) a collection of comics, will feature a story arc of 4-6 issues. Sometimes there is extra artwork for more history or background information.
Online retailers
Amazon, B&N
Local retailers
B&N, Comic Shop Locator
Amulet, 1
Katie the Catsitter, 1
Mermin, 1-4
The Big Bad Pizza Battle