OK:
[sblock]
(1)In the books, Jon Snow sends a fleet to Hardhome to evacuate Free Folk refugees, but they get hit by weather and a Zombie attack. Snow isn't with them.
(2) In the books, Jon Snow convinces Mance Rayder to bring all the Free Folk inside the protection of the wall, which he does (minus some who turn away, and the ones who run and get trapped at Hardhome.
The series combines the two events in a way that enables #2 to occur while simultaneously showing #1, and having Jon Snow both be a witness and a way to get the audience more emotionally involved. The series shows the risk of the Wildlings falling to the Others, where in the book Jon Snow just talks about it. It's much more powerful when edited this way, IMO.[/sblock]