(Truth be told I wouldn't even attempt to walk up those stairs. If I'm faced with them in real life I'd probably take one look then decide I'm better off downstairs, or just decide to crawl up and hope no-one sees.)
As previously stated, this is a photo of them from the top looking down and there would not be a slant when walking on them.
These are said to be ergonomically correct stairs as you can only walk up and down them in one way (always starting with the right foot) with less risk of tripping up or falling down because there is no middle-step to clear with the foot that has to swing forward. It would take some getting used to at first and using wood is a terrible idea because you would indeed slip around with socks on but in theory and apparently in practice they work far better than conventional ones!