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 Genius of America has 269 pages.
Genius Squad has 436 pages.
The Selfish Genius has 240 pages.
Advanced Genius Theory has 288 pages.
A Heartbreaking Work of Staggering Genius has 375 pages.
Not That Sort of Girl has 279 pages.
The Cave Girl has 323 pages.
A Girl from Lübeck has 216 pages.
The Girl Hunters has 218 pages.
The Girl in a Swing has 339 pages.
The Danish Girl has 324 pages.
Third Girl has 256 pages.