It depends on what copy or version you get; the paperback is 272 pages while the hardcover is 256 pages. This is due to the text size- the content does not differ from one book to another.
The Selfish Genius has 240 pages.
Genius Squad has 436 pages.
The Genius of America has 269 pages.
Advanced Genius Theory has 288 pages.
A Heartbreaking Work of Staggering Genius has 375 pages.
The It Girl - novel - has 272 pages.
The Italian Girl has 224 pages.
Third Girl has 256 pages.
Twenties Girl has 432 pages.
The Danish Girl has 324 pages.
Ladybug Girl has 40 pages.
The Unwritten Girl has 208 pages.