You find the tomb entrance in a cave opposite the spot marked by the game (the cave location overlaps with the dots that represent the zipline). Inside, remove the obstacle using the rope arrow and follow the path to the camp.
Past the campfire, go a bit to the right and walk between the rocks. Then, jump over to the other side, climb up and grab onto the climbing wall. Follow the only possible path, jump over to the other side and walk along the ledge. You will then get to the tomb proper.
Then, from the spot shown in the screenshot, jump up ahead and grab on to the ledge. Shimmy a bit and drop down towards the wall that you can jab your hatchet into. Watch out here, because Lara will slide down the first wall and you need to grab on to another one, during the ride. Over the wall, reach stable ground (you can go left here to return for a Relic and a Survival Cache). The way ahead is along a narrow passage that collapses - be prepared to grab on to a ledge once again. Jump to the right two more times and you will get to the entrance.
Pick up the Explorer Satchel, and a Survival Cache next to it. Also, you can backtrack a little, where you find the Relic at the end of the path. Then, walk inside. On the left, you find an Archivist's map and a Document, near the door up ahead, there also is a Survival Cache. Finally, use the knob to lower the gate. Over the gate, you will get to the upper ledge, from where you need to drop below, by the hoist (a Document next to you).
Attach the weight to the hoist. Jump over to the ledge on the left and destroy the wall, then turn the mechanism by the gate, which lowers the weight. Return to the hoist and tense the hoist line with the weight hanging on it, as much as possible. Now, whet you need it timing. At the other side of the hoist, there is a lever that you need to pull at the right moment to make one of the weights hit the other one and shatter the ice lump. The right moment is when the wind is blowing. You know the wind is blowing when you hear it, and visual-wise, it is when dust is blown inside. As soon as wind starts blowing, release the weight. If you do this correctly, it shatters the ice cap at the other side.
Now you need return to the main chamber and open another door. Behind the door, there are stairs that you climb to get to the book.
Reward: The "Inner Strength" ability (health regeneration, if you sustain critical damage, once per fight).