If that is a standard sharpie, the book is about 9.6" tall x 9.9" wide. That means it's a middle size book, not tiny. 
A mouse pad is ~9.5" wide, so imagine if your mouse pad was square. (maybe larger if the sharpie is further away, but it is in focus, so probably not significantly larger than my pixel calculation)
Sharpie = 11.4mm thick
------------------------------
HEIGHT CALC (first image)
17x12 =20.81 diagonal pixels sharpie
446x25 = 446.7 diagonal pixels book height
11.4 H
--- x -----
20.81 446.7
244.71mm tall =9.63 inches
------------------------------
WIDTH CALC (second image)
32x468 = 469.1 diagonal pixels tall
511x12 = 511.14 diagonal pixels wide
9.63 W
--- x ----
496.1 511.14
9.92" wide
