Based on the extremely popular Koren Sacks Siddur, the Koren Shalem Siddur is a new, enhanced siddur that includes the entire contents of the Sacks Siddur AND: 
All Torah readings with new translations for the Shalosh Regalim and Hol HaMoed, Hanukka, Purim, Yom Ha'atzmaut and Yom Yerushalayim.
Modern English translations of the Five Megillot.
Additional personal supplications (tehinot)
For ease of use, and to facilitate adoption in synagogues and schools, the Koren Shalem Siddur maintains the same pagination as the Koren Sacks Siddur..