At the start of the level go left up a ramp.. it's behind some garbage.

After you geft the goggles off the broken WALL-E unit look to the right. There is an unobvious ramp leading up to the sketchbook.

After the first vending station, hop across the sludge

In the secret area: to your left (from the starting area)

Above the fountain, use a charge cube to start the fountain and hop in the water to be boosted up and reach the sketchbook

To the right of the fountain, jump on the boosting platform to be boosted to the sketchbook itself.

To the left of the fountain is a giant ramp. Lower if you stand on it then reach book at the top.

Straight from that where the tires start to roll is another boosting platform. Jump on the platform to be boosted to the sketchbook itself.

At the end of the tire section: Vending machine.

Take the large ramp that leads up to the bouncing platform with several traffic cones on it. The book is somewhere there.