is it necessary to play the other thief games before this?

[phadet]

or i can still get the story from this game?

[jack_of_tears]

No, you'll probably enjoy this game more if you haven't played the classic and much-beloved originals. Once you're done, however, I encourage you to look up the cutscenes on Youtube in order to understand the original story of Garrett.

[Eternie]

If you want to play the older games at one stage It is still better to play them in order, as going backwards in any series always just disappoints as your always comparing and the older ones have dated graphics.
They were brilliant at the time in 1998, 2000 + 2004, each as a new game when released and could be recommended to play if you want to learn the lore about Garrett the master thief, Basso Viktoria and the Trickster.

Each has levels of difficulty that they can be played with and tutorials to learn the gameplay and keybindings used.

Whereas this thief released in 2014 has way better graphics for cutscenes and can be configured for how you want to play it, far more than we could with the older games.

:edit The Thief series bundle is on special at steam for ~$4 with the first having a gold remastered version.