This is the 7618th most frequent Turkish word.
hepsinde
"In all of them."
'Hepsinde' is used here to indicate that every book mentioned contains beautiful pictures.
Kitapları çok beğendim; hepsinde güzel resimler vardı.
I liked the books very much; all of them had beautiful pictures.
'Hepsinde' emphasizes that each person in the group of friends possesses unique abilities.
Arkadaşlarımın hepsinde farklı yetenekler var.
All my friends have different talents.
'Hepsinde' shows that every dessert individually had a distinct flavor.